I own a full 5.1 of the LSR series and it's super clear, even at low volumes for late night watching.
Check out the owners threads for satisfaction on both. There are lots of people who own the JBLs here at AVS and are very happy with the sound.
I use an ASUS Xonar U7 usb sound card with it and it sounds great. But I also got some baluns (balanced / unbalanced converters) called CleanBox Pro so I can use XLR cables from a long distance. The 1/4 inch direct RCA sounds fine too, but there's a slight hiss. When you run the speakers at -4 db (pro = balanced line level) they sound cleaner to me. But they sound perfectly fine at +10db setting for direct unbalanced mode. I'd start with that and add cleanboxes later on.
I got the 308s and 305s in the rear. A sub is a good buy regardless. Even a super cheap one for now. I got the 310S JBL sub that goes along with the set and that is terrific too. I like having a full set of the same manufacturer. The sub is pretty good because it accepts two line ins for your stereo so you can run the 308s through them and treat them as full range speakers without even using an AVR. It's a great option for 2 channel music.