everyone says wireless but there's a reason high end systems use cable that can run as much as a grand for a 5ft section. wireless is convenient but it'll never be as clean as wired imo.

cig, in the end you need to ask yourself what do you really want.

are speakers fine, if so just replace av receiver and done.
if speakers are not fine(or just tired of them and want something new) then ht in a box is probably going to be the easiest and cleanest replacement for everything(including bluray) and will fit within your price requirements. now if you were going to spend a grand, I'd say go separate receiver and get a 5.1 speaker system. if you listen to music at all, get a solid set of fronts and a matching center and a small set of rears. if only for tv, then a matched 5.1 system from polk, denon or the such would be a great setup. on one hand you mention not watching a lot of tv, but then are going to go from 46(a great size) to "55 or so" so guessing tv watching time is somewhat important so I would really ask what your end goal is and go from there. if tv time is important, I'd tell you to rethink the budget and perhaps do it in stages. receiver now and speakers later if you don't mind the jbl's for a winter.