Personally, being a daily, I wanted the auto and the RB26 engined Stags (the 260RS's) are all manual.
Knowing what I'm like with the 32 (clutch-stab happy lol) I didn't want to get a big heavy 4wd car and put more power through it as it would eat clutches for breakfast unless I drove it a lot nicer than the 32.. but where's the fun in that?!
The Rb25 Neo is a nice engine and has a lot of potential, it just needs a bigger turbo. Whereas with the the RB26, the stock turbos should be able to make you nearly 350rwhp.
Horses for courses really, if you have a toy and this is just a daily, go the auto S2. If it's a compromise with the mrs so you can still have a fast family car because she won't let you have a toy, get a 260RS.
As far as buying with mods, that's completely up to you. If the mods are done well (the mods to my car were all done by a reputatable tuning shop over here at the previous owners expense) then there's nothing wrong with that. The main reason I bought one with all the mods done was that I already had a toy car and it was coming off the road to do more stuff to it, hence wanted a complete turnkey daily package