The more displacement you have the easier it will be to reach your goal. A 2.5L hybrid isn't any more detonation prone than any other engine if it's done right (combustion chambers should be worked over, deshroud valves, more volume, etc). That said, I hope you're not planning on trying to reach those numbers on pump gas. The size turbo it will take to make that power on 93 without AVCS will mean you're not going to spool till 5000rpm or later. On the 2.1L I wouldn't expect it to have any power till around 5500rpm, then it's time to shift to the next gear. Not very practical IMO. If you have easy access to e85 it's a different story. You could be at 500whp and hit full boost around 4300rpm with the right build (2.5L) on e85. Meth is also an option if e isn't available.
That power level isn't going to be the most reliable, the car will need some degree of work on a monthly basis. You could take it on short trips, but don't be surprised if it needs to be towed home every once in a while.