If you are recording acoustic stuff, the mic is most important. After the room. Because the more "air" you are able to capture the more room you get. Since you haven't said what your budget is, it is hard to advise on what to buy. A good chain (mic/preamp/convertor) in a good room will most likely sound better than a great mic in a bad room. They all act in consort together.
In general, you pay more for a "tube" unit than solid state. If you are on a budget I'd steer clear of tube stuff as first buys. If you are looking for "character" that depends more on transformers/overall quality of components than tubes. I'm not familiar w/ the vtb 1 - I don't know if I've heard one and haven't used it. It is tube based, but I think it is a strarved plate design. But in general, again, the reason to upgrade a preamp from the transformerless ones in the standard interface is gain more than anything. W/ high gain you have more choices in mic placement, and backing off the mic from the source, which gives you "air" which makes the instrument sound more real. It is a cycle, vicious if you don't have a clump of money or assurances you a stream of it. Character comes from the components, which come at a price. If you need an outboard stereo pair there is the M-Audio DMP and others I'd choose before the vtb 1 unless you can get it cheaper. If you want a premap that means never having to say sorry to your song, the Warm Audio preamp runs about +$400 and is the older APi 312 design and sounds vintage w/ more gain than you'll ever need. The Focusrite ISA One is a tit more expensive w/ a more modern tone (though still w/ a nice transfomer than adds thickening and a saturation sheen if you want). Both are preamps you'll never need to get rid of even after you top the charts.
Mics are all over the place. But the same principles apply as preamps. An sm57 is a must if you record amplified guitars. For vocals, any good large condensor will work tho might not be the best choice for x voice. For other acoustic, unpowered sources, a (stereo) set of small diameter condensors are a good choice. They work well on female voices too. If you are strapped for cash, look at the mics that are commonly modded, which can make them much better and you can do that when you replentish your cash. I had Joly mod an old Oktava 319 I dropped and it came back twice the mic. Not a Newman or Gefell, but closer. The AKG C 214 is a good buy, from what I've heard. Goldilocks - not too bright, not too dull and a good all-arounder. Like most everything recording, I prefer to get something good enough I'll keep rather than 2 things I'll end up questioning after the excitment of new toys wears off.
And sorry, I don't know much about power amps. Been using the same speakers/amp for 30 years here at home. But you already seem to know the basics - don't buy frills. And get as much power as possible - most speakers are blown because of underpowered amps reaching their limits and sending clipped signals to the speaker.
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post edited by AT - 2012/11/27 11:08:10