Mr. M,
I 2nd, 3rd and 4th the suggestions that you shouldn't worry about the magnets on your speakers. I think I read that same 3M article or something similar and the article I read detailed the flux level emanating from a degausser and that, while we use the rule of thumb to turn on and off the degausser at least 3' from the transport, the effect doesn't start kicking in until inches from the transport...magnets from speakers, even big ones are not going to have as strong or far reaching an effect as a powered degausser. I betcha 2' is plenty fine for your tapes and 3' is just overkill but that's the rule of thumb I follow because I am comfortable that it is safe.
You can use
anything for monitors. The important thing is that you have some sense of what they do and do not reproduce well and what their "personality" is, okay? That's my 2p on the subject. What distinguishes "studio monitors" is that they strive to have a flat frequency response and to cover a wide berth of the frequency spectrum so you can hear what is going on and won't be surprised when you take it out to your car or try it on your buddy's home stereo or listen to it on your mp3 player/boombox/laptop...headphones...whatever. If the speakers do a good job of covering a good deal of the audio spectrum (and I think the lower frequencies is where you typically run into limitations), then, like has been suggested, listen to consumer music on the system once you get it setup...listen to stuff that is good quality production material and with which you are familiar...the idea is to
calibrate your ears in a sense to your monitor system. Example: I do have a set of "studio monitors" and I learned during an early project that, vocally, what sounds mellow on the monitors comes out sounding pretty right as far as character balance in most other environments...I was mixing vocals with too much cut (2~3kHz) so it would come out of the mix...bad...painful in some environments. Does that make my monitors bad? Maybe my ears are just tuned that way, so by learning this I just make the vocals sit back in the mix a bit more and make sure they have a softness to them...it doesn't sound "right" to me in the studio, but because I now know that that sounds "right" elsewhere that becomes my new "right" in the studio...that's calibrating my ears (and brain) to my system. No reason you can't do the same with your system. Now, if you were an engineer and you worked in many different studios you'd like it if things were somewhat constant as you move from environment to environment right? Not possible as every room is different and every set of monitors is different, but having a standard goal of "flat" response for studio monitors helps to narrow the variations. But that doesn't mean you can't use whatever you want in your own studio and I'm guessing your speakers do a good job reproducing the low end. I find home speakers to be a bit more mellow sounding over all...lacking some clarity in the upper midrange but that's not a deal-breaker at all.
And, yeah, I saw your plan of putting them off to each side and I said "no-no-no-no."

I don't mean that to sound judgemental at all. Very glad you feel this is a place to put that stuff up to get opinions as that's one of the best ways to learn. The fellas are right...think of the soundwaves coming off the speakers and if you have them facing each other like that then those waves bounce back and forth between the walls and your head is in the middle of the wash and things will smear up on you real quick...frequencies will be either augmented or all out disappear on you due to phase distortion.