I doubt very much if you want a Powercore, they are way too loud.
I ran my WRF race bike with one for a long time, OK for racing but not acceptable for trail riding, even with an insert.
The Q4 would be fine, would derestrict the TTR motor without causing the offence.
The Q4 sounds "proper" and would probably run fine without jetting change.
I would have used the Q4 for racing but couldnt find one and new was out the question.
I run a powercore 4 with a decibel reducer, sounds sweet and considerably quieter than most standard KTMs.. The bonus being the exhaust with reducer was ££££s cheaper than the alternatives :) mines fitted to CRF..
I paid £150 for mine used for a few miles.. it got delivery in original box with reducers if required, accessories.. even stickers! wasn't even coked..
Peeps buy the powercore 4 and then think its too loud and sell it on... Get yourself a bargain!
Will post a vid of the standard exhaust Road going CRF250L then with decibel reducer baffle and then again with just the decibel reducer.. it may help you decide..