I have a UA 4-710d Mic Preamp and it works well for many of my recording needs, such as vocals and electric guitar, but it seems to have a bit of a noise floor when I record classical guitar (or even steel string acoustic).  I'm running a pair of SDC mics (Studio Projects C4) and when I turn up enough gain to get a decent level out of the preamp the noise is just a bit too high.  I'm looking for suggestions on something that will be better for classical guitar.  I've been looking at the Grace Designs m101 and think it might fit the bill, but thought I'd ask here for anyone with experience with both pres to see if it:
A. Has a significantly lower noise floor
B. Sounds better for a clean nylon string classical guitar (the 4-710d has a bit of color, so I think the clarity of the m101 might be good here.)
 
I'm also looking for any other suggestion on lower-noise good sounding pres.
Thanks

The industry standard for classical pres is the Broadhurst Gardens No. 1 by DAV.  The preamp of Decca records.  They are actually quite affordable also.  
 
http://www.davelectronics.com/products.htm
 

Actually looks like a pretty nice one. Thanks for the tip.  I sent an inquiry to them.

Something to consider with this is also your recording environment. The body of an acoustic guitar will resonant environmental noise as readily as it will a string. The sensitivity of a microphone and chosen placement can exacerbate this. Gates and noise reduction utilizes can be useful in a scenario where the noise floor can be recorded discretely (like a few seconds of "environment only" before and after each take).

Your cheapest way is probably a focusrite ISA One.  Lots of gain, a single transformer so it is clean but not too clinical, and plenty of do dads (if you find them useful).  You can find them for $400 knew - or less on used on Ebay.  It is a great sounding preamp for what you want.
 
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for a clean preamp, I'd go with a True Systems P-solo (which I own one of and it is truly very clean) or a Grace M101, which I would like to have because it's rack mountable (the p-solo is not).
 
I haven't used the grace myself, but I've heard recordings made with them and they are very clean as well.  either of them will give you simply true gain with no color.
 
The P-solo is about $600  http://www.sweetwater.com/store/detail/PSolo
and the Grace is $740 http://www.sweetwater.com/store/detail/m101

I bought a Joe Meek Three Q a few months ago and it was a wise purchase. I read a lot of reviews and it was either it for $230 or the Warm Audio which was $599. I'm sure the Warm is better but so far I've found no fault with the Joe Meek. It is dead quiet too. I've used it for  Vocals, Acoustic guitar and Bass. 
 
http://www.joemeek.com/threeq.html
 
http://www.sweetwater.com/store/detail/TB12
 
 
 

I GOTTA SAY,
 
the A Designs 500 series,
especially THIS one:
 

would be a good way to go
 
http://www.adesignsaudio..m/500-series-mic-pre.htm

If it were me I'd go with either the Grace Designs or Millennia Media preamplifiers. Both companies offer many models, probably one that fits your application and budget. Both are clean, quiet, and built to last forever. I'd have a difficult time picking one as better than the other, they do have different sounds, but both are fantastic neutral microphone preamplifiers, very nearly "wire with gain".

Thanks for all of the great suggestions. Been reading reviews and spec charts for the last couple of days and would probably have gone with the DAV, but it was just a little out of my price range.  If I had a bit more of a budget I'd probably go for that or a pair of m101s for the clean pres. 
 
As it came down though, I missed a deal on a Grace Designs m101 because I didn't bid high enough... found a pretty decent deal on a Focusrite ISA Two, and really need two clean, quiet channels anyway, so I snagged it. From the specs they look to be quite a bit quieter than the UA, here's hoping it sounds good as well. I have the UA for a few channels of color (although I'm considering putting it up for sale and getting one really nice colorful pre instead.)