The 'green pre' project looks pretty nice, although the choice of a discrete BJT with the 5532 is an odd one, FETs would be way better to use, higher impedance and lower noise...that one has a balanced line driver on the output too, but I didn't think that was really necessary because most people use short (or super-short) cables to go from their pres to A/D or deck...the V2 has a nice line driver in it too but it's for doing a remote preamp setup, which is basically a niche application for permanent installations or venues etc. I was also thinking about doing a swept gain setting, because doing the switched attenuator is kind of a bear to do, but it's a better solution...you can't use a standard pot to replace the attenuator because it requires a really goofy (nonlinear) curve to have a constant gain reduction per degree of rotation, so to do it you'd have to fix the gain of the amp and use a pot as a voltage divider after the gain stage - a bit noisier but also a bit easier to operate and trim in...still an option at this point tho.
the guy who posted the 990 comment, a 990-type discrete opamp would be really bad for a battery powered pre because of the power dissipation, those are usually class AB or (gasp) class A so they're burning off 75% of your battery power as heat - think AD-1000. Transformers are nice to use, but they are what they are...expensive and fairly large but inherently DC blocking and bandwidth (noise!) limiting...one jensen transformer costs as much as 2 channels of my pre including board, parts and all...