I know no one's talking about the Audient iD22. Not sure why. It's an awesome unit. But just so you have some information, here: http://tapeop.com/reviews...2-usb-audio-interface/

Jim Roseberry
Babyface pro is also a great choice (anything RME is excellent).
 
At the $650 mark, nothing beats the MOTU Ultralite AVB (performance, sound, flexibility).
 
As a point of reference, most audio interfaces at or below the $500 mark have an average noise-floor of -103dB.
The Ultralite AVB has an average noise-floor of -112dB.
That's not far off from the RME Fireface UFX... which is a dB or two quieter.

 I looked at this. Nice peice of kit. I don't like that the second mic pre is on the back though...almost like an afterthought. I usually track two mics in stereo. Simple work around with a short XLR extension. At least it has another mic pre. Lots of I/O in a small package.I would have preferred two mics pres on the front, but that's me.

Interesting that you mention Lynx.  They have the e22 and e44 now, pcie.  I do have a couple pcie slots open.

yes, they are a tad pricey, tho.  I have no idea about their noise floor or latency of their drivers.

So I ended up with the Tascam celesonic.  Working great so far.  I've been working with a gazillion plugins as well as many samplers with no latency on 64.  I'm afraid I'm not much of an audiophile so can't give a reliable review of it's sonic qualities, except that it's perfectly adequate for my purposes.  Latency was my big bugaboo.