I'd probably go with the BMW. It weighs a little more than the SRT, but it also has roughly 375hp (despite BMW's claim of 300). It takes just as well to mods as the SRT, has a larger aftermarket, and is more practical. The only real drawback is that they're almost as common as Mustangs and they haven't stopped plummeting in value.

As someone else mentioned you should go for an E46 M3. You can get all of the benefits of owning a 335, but pay the same price you would for an SRT6.