^^^I do believe there is more aftermarket support for DSMers than a srt4, but then again I dont really follow srt4s, You can have anything done to a DSM your pcket book will allow. Not sure that srt4 can say that quite yet.
actually you can. from the factory with a warranty. if you do get the srt-4 (don't know why not even one of your choices), but get the stage 3 upgrade for the car and it will be putting out around 400 hp. OF THE TWO THAT YOU MENTIONED I would get the 300, but that's because I'm a nissan guy and not really bothered by the reliability because once you get the VG going it'll be a beast.