I had considered the SE-R Spec V, I have had great experiences with nissans and infiniti's in the past. The problem is the QR25 just doesn't have enough strength to it. I still checkout the forms on b15sentra and a few others, and it looks like the forcedinduction kits are currently around 4-6lbs of boost, no clue yet on the JWT kits. Aside from that, the kits will cost a pretty penny. The one thing I've learned from owning a naturally aspirated car (my current z), is that when you buy a car with a stock turbo you save a ton of money. You can always start with just cranking up the boost a bit (within reason), and when you want to go with bigger turbos or other parts, the plumbing is all still there for you to use. I believe that the srt engine is much stronger than the qr25. Like many I was concerned that there wouldn't be much room to mod it, with stock boost between 11 and 15lbs.
But already there's a lot you can do, and more coming soon. You've got the mopar upgrades, the atp turbo exhaust setup and exhaust depot's exhaust, there's boost controllers, you can put a co2 setup on the intercooler, remove balance shafts, put in new engine mounts, etc, etc, etc
All told, you can go as far as your checkbook will allow.