I've got the RME QuadMic which includes the same preamps but without the AD conversion. I just posted in another thread that the preamps aren't going to win any shootouts against the $1000/ch models, but for just over $100/ch, they are certainly useable - and at least as good as the transformerless preamps in a lot of low or mid-priced consoles.
I regularly use them on the same job with better preamps like API 312s, Siemens V78, 1272s, etc., and on the right source, with the right mic, the QuadMic preamps rate at least OK, if not pretty good. To get a significant increase in performance, you'd have to double the price to around $200/ch and go for the Sytek 4 pack.