Congrats on the great purchases. I'm a huge PSB fan myself and that's what my HT is made up of. I'd say go c40 so that all your drivers match and you save a little dough, both centers sound great though.
PSB makes some great subs, but they do tend to be a little more $$$ than some of the competition. Also they rate their products very conservatively so the ratings they give may not look as impressive as a sub they will out-perform. That said the SVS subs are supposed to be just killer and you would save money going with one of their entry level subs like the PB-10. Room measurements would help to determine what size sub you need. There are several brands of sub out there though, so don't limit you're search to just SVS and PSB. I haven't heard any SVS subs, but I'd think they'd make the better buy between the mentioned brands if you are in the US. If you're in Canada I'd say HSU. I have heard HSU subs and I think they are a real bargin up North.
That JVC is really underpowered for the task IMO. If you plan on playing music and movies at reasonable volumes in a small to medium sized room while you wait to upgrade you'll be fine though. Just don't crank it up to the point where you let clipping set in. The PSB's you have are not the most efficient speaker out there (not a bad thing at all just means they like the juice) and you should notice an improvement when you step up to a more powerful receiver.