The warm preamp is more vintage sounding and not tube-based.  In my experience, it is the transformers not tubes that give most of the sound people talk about.  And, of course, the old tube stuff used transformers, too.  The ISA is a solid, middle of the road preamp to my ears, and for the price comes w/ a lot of extras you may or may not find useful - headphone, preamp and DI at once, inserts.  It rounds out a sound a little w/ the transformer.  I prefer the warm to it, but perhaps not for vo work.
 
@

Glad to hear your views on the Re-320.  It seems like the real deal, but one always wonders.
 
@

The RE-20 is a great example of a mic that needs a good preamp match to open up and sparkle.
 
I have an old Ampeg radio booth mixer preamp and it has the plug in "can" input transformers. I forget the specific labeling, but I remember when a mentor brought over a particular transformer can and we plugged in to the Ampeg preamp's socket for that channel. It was sort of amazing to hear the RE20 come alive and sound lively. It sounds reserved and safe when you run that mic through a Mackie and it sounds hi-fi and articulate when it runs through the preamp is was made for.
 
:-)
 
Here's some too-much-info for folks who like this sort of stuff:
 

AT
Glad to hear your views on the Re-320.  It seems like the real deal, but one always wonders.

Prior to hearing it, I had doubts that the RE-320 would be equal to the classic RE-20.
After listening side-by-side, I have no qualms about the RE-320.
Very similar character to the RE-20... with a presence boost in the upper-mids and hotter output.
With the Ndym magnet, these differences are exactly what you'd expect.

<edit>

Here's a footnote for your next book:
 
"Alctron Electronics Co., Ltd , is located in Ningbo, close to Shanghai in China."*
 
:-)

No books today Mike :).... 
 
Here is where I got some of the info on that pre amp.
 
 http://www.gearslutz.com/board/so-much-gear-so-little-time/714017-alctron-mp-100-a.html
 
Hence my confusion the Aussie seller must have been simply a distributor. My bad.
 
 

That Twin is Q a very class looking act there Dave. The reason I asked about it is because the newer models apparently are not made the same since the company was bought out. I wondered how big the difference was. Since I haven't gotten too deep yet into anything colored I'm not sure what I'd be getting myself into. It must be one heckuva nice unit to use for guitar. I'm guessing a little heavy in the mids.
 
The Twin Finity looks like a steal for the capabilities it has and I'll admit to looking at the logo too in making that assumption. It might be my next pre.
 
After spending some time with the MPA PRO 2 yesterday I am happy with my purchase. Plenty of gain. I went out into my interface with XLR at +4 from the MPA . Once I had the gains set correctly there was plenty of good clean gain. I thought it was noisy until I realized that the noise was mainly coming from my headphone amp. Driving it high made it noisy but I never intend to drive it that high which would be too much. As it was I had plenty.
 
I am missing a compressor though. I tried vox and then went direct to try bass. I tried to compress ITB but there was too much delay. If I deactivated my other interface channels I think I could get the latency to a better place. The MPA really does well on bass and vox, but I did have to be careful going in not to go in too hot. For bass a simple compressor pedal would work. I didn't really need to compress vox. It would probably work well with any source.Not sure if I'll mod it or not. If it makes a huge difference then maybe I'll drop in tubes, but then I won't know that unless I buy and try the tubes.