Your 4033 is a very good mic [IMHO] for recording elec guitar
and can be pretty good for vocs. too. For acoustic It can be ok.
So I dont see a reason to drop alot of cash on a mic at this point
Learn what you can do with that mic first..then see what you need later.The gotta have a tube thing seems like a hold over from the days when digital recording was newer ,everyone was trying to soften[ harmonic distortion] there input into the recorders to emulate analog machines.I'm not a expert but thats
my opinion.Now the equipment is better {a/d converters,higher bitrates}.There are so many options for mic pres now that you should look into all the different ones avalible They all have different sounds .If you are going to spend your cash try and be as vesatile as you can ..And you didnt say anything about a compresser,
fit that into your expenses you will want one to track with one.
The RNC is a good value under 200.00. I hope that I helped you
some.....Good luck
Don