How much $ did those mods cost?
Almost nothing... The JB4 tune costs $500, $100 for a dual cone intake and that's probably where 80% of people stop. Add downpipes ($500- $800) and a larger front mount intercooler and you've basically done all you can with the stock turbos.
Realistically though, a tune and intake alone should have you knocking on 12's. Add E85 to that for some extra kick.
I'd go with the 535 if it's going to be a family car. The 3 is nice but you give up almost nothing by going to the 5. Just make sure you go with a sport package.
I'd also skip the Xi model. Just get a nice set of winter tires. The sport version of the rear wheel drive models is by far the best handling. Sport Xi's are basically appearance packages and that's it.
You can find some really nice examples in the OP's price range too.