The PV1 will far outperform your Bose 'bass module', but it'll depend on the size of your room as to whether it'll be a good choice or not. If your room isn't too big, it'll be fine, but if you have a large room, there are plenty of subs out there that will do a much better job of pressurising your room. Try the Monitor Audio GXW15, KK Sound MX700 MkIII, or the SVS PB12 Plus.
As for the speakers, demos I've done so far have had people saying that the CM9's are fuller with a 'better' bottom end, whereas the GX200's sound a little 'thinner', but are easier to place because of this. In an AV system, the lower end doesn't really matter as the sub takes care of it - it's only an issue if you'll be listening to music in 2-channel mode without the sub.
I have to agree with Cno's choices for AV speakers. The KEF R series are probably one of the finest ranges of -fi speakers that do a great job with home cinema, mainly due to their UniQ drivers, offering a more accurate soundstage. Give the R700's a try against the MA and B&W and see what you think. The PMC Twenty range is also up there with the best - they're lighter in the bottom end, but very insightful.
As bigboss mentions, Ken Kreisel is releasing a new range of home theatre loudspeakers, but unfortunately we're a couple of months away from the release of the first speaker package at the moment, but more will be following over the remainder of the year. Judging by his original Miller & Kreisel designs, his forthcoming updated ranges should elevate them above hi-fi speaker packages for the reproduction of movie soundtracks. Details will be announced as soon as possible.
Any of these packages will be an enormous upgrade over your Bose package, and your LX81 will be fine for driving any of them too. If I were you, I wouldn't mix and match with Bose - if you're going to ditch the package, just do it in one go. Even if you had to go without rear speakers or a subwoofer for a bit - with speakers like the above, the Bose won't bring anything to the table.