Man, yeah I'd never hire an installer, but that's me. I'd rather do it myself and save a few bucks. I also agree with
@William Lemmerhirt on the "sealed equals tighter bass" thing. A well designed ported sub will sound just as tight and play lower with more power. The only clear advantage I see going with sealed is if you're tight on space and have to have the smaller enclosure.
I think a pair of PC2000s would give you what you're looking for and they're a little easier to place than a big box. Have you looked into any other manufacturers? I love SVS but their really good stuff can get a little pricey. Normally I'd suggest Hsu also, but I actually read enough og this thread to see you're located in England, lol.