There is quite a bit that you can do to perk up the '6. The best bang for your buck would be to:
1) Add a dual cold air intake
2) Get a 62 or 65mm supercharger pulley
3) Get a tune

These basic items will add 50-60 HP to the car and are not that difficult to install. If you plan on taking it to the track a lot, you want to upgrade the differential to a Wave Trac.

I have owned SRT-6s since 2011 and have had no major mechanical issues at all. You won't regret it if you buy one.

The forum has a ton of information, so I suggest doing some reading if you are looking to do a particular mod.