the ISA preamps are great. I just ordered a second 428(4 channel version) so I could have 8 channels of ISA pre's. I use them side by side with API's,great river and Neve. and they hang right there with them. not as colored as the other ones but not as noisy as the Great River or neve's either. way under rated IMO
if you want something with a more colored sound check out the GAP Pre73. but the isa is slightly colored,def not super clean like grace or true.....ISA's are great and really helps tracks sit in the mix. and if you get the one with the Digital option you have great a/d conversion too