A few clarifications....
Rev E, it would seem that Alesis changes their tune on the Masterlink box. In that thread long ago, I ask the Alesis rep to tell me WHAT the internal processing was. He didn't know, and went to Alesis and came back with a 24 bit fixed answer. Later, on Alesis's website, they claim that their box actually does 40 bit internal processing. Maybe the bit depth "increases" to 40 bit before being dithered back to 24....

Who knows. That being the point. Who knows....
Next. Computers work on a 32 bit floating point dsp scheme. THAT is equal to 24 bit fixed dsp roughly. Some software works on a "double sampling rate" scheme, which is hard to find any information about, but it is something to the effect of producing two samples of every "actual" one for the processing to be applied to, then it is "sampled back down" to the original sample rate. Steinbergs
QMetric mastering eq does this, and it is an exceptional sounding digital eq to my ears.
odiwgal, if you are working with classical music ensambles, I would stay away from ANY digital mastering that you would do yourself. That is music that simply does not need "mastering" in the sense that Popular music does.
Okay, let me clarify even further what I mean. There are many components to the modern mastering process. Eq, compression, song to song overall level adjustments, cross fading between two songs, fade outs at the ends of songs, fade in to songs, and of course the old "hidden track" at the end of a CD. Any or all of these components COULD be applied to a collection of songs that will be on the same CD. I say COULD because you may not have to do ANY eq, compression, or song to song overall level adjustments. You may not have crossfading between songs, etc.....It really depends.
The reason I said earlier that maybe you should start doing it and experimenting is that you will not know what you need to do until you see what you CAN do and hear the results.
With classical music, the most I would consider doing to it if I was mastering the project is placing the proper amount of time between the songs, and cleaning up any noise before the piece starts and after it ends. That is IT! No eq, no compression, no song to song level adjustments. ANY of that stuff you do is going to create problems with the original sound if not done with the highest quality equipment. In classical music, it is all about the sound being "natural". The techniques used in recording it are all about making a microphone catch the performance as close to what your ear hears at the performance as possible. Eq and compression are seldomly applied, and usually only because there is a severe problem that needs to be addressed.
So, I guess what I am saying is that of any music style there is, classical is traditionally the one that doesn't get the hard core treatment in mastering. For that style, song order, a few noise problems, and space in between songs is what is usually applied to the original "mixes" of it in mastering.
Hell, for that, you could use Goldwave. It is about $40 and works very well.
Don't go messing with those beautiful sounding acoustic instruments. If it don't sound right at mix, you messed it up while tracking it, and no amount of eq and/or compression is going to make it sound right again. If anything, eq and compression on the instruments in classical music with make things sound worse.
My opinion. Take it for what it's worth.
On a side note about mastering. I believe that mastering is a culminization of the whole recording process. Without a great handle on eq and compression, and keen insight into the benefits/drawbacks of it, and a pretty good handle on obscure stuff like dithering and what not, it is best to just leave your product alone. I have yet to really post much about the whole process of mastering because it is hard to articulate because you don't have to do the same thing twice per se in a mastering process. It is very involved to do it right, and takes a lot of explaining. Any engineer who has done it or seen it done knows what I am saying here.
I believe great results can be achieved with the "less then" equipment, but that of course requires that you really know what you are doing with it. I don't suggest however that a person with no idea what they are doing could produce great results with all the best gear just because they have the best gear.
If any of you really feel you need to learn the art of mastering, it is quite simple, find a mastering engineer who you feel does a great job and hire him/her to master a few projects for you and sit in and watch what it entails and hear what they hear. This will be an expensive learning process, but you will learn a lot from it. Tis' how old sonusman learned to do it.....
Anyway. Software or hardware.......Software for sure. Wavelab on a PC for sure. Waves plugin's work nice. Hardware for the same price? Well, be advised that you will wind up running that mix back into the computer to author a Red Book Standard disk complete with PQ timesheet, so why bother with $1000 or less hardware? That is money better spent on plug in's that will do that same thing. THAT is what I didn't like about the Masterlink. Also, like RevE said, plugin's can be upgraded, and new ones can be bought.
Top end analog gear yields the best results in mastering for eq and compression. Anyone can argue all they want, but there is a perfectly good reason why most mastering for top artists is done with analog gear.....you know what I mean? I have heard the difference with my own ears too, and the analog processing route is the way to go for the best results. But it is very very expensive. The next best route is software plugin's. Some great one have already be named.
Good luck.
Ed