My issue here is not with the speakers as such, I'm a fan of value for money as well and have several budget setups with me. But my issue is with the way you are distributing available funds. If you have 500$ set aside for an audio upgrade, you arent going to really benefit by putting it all down on a good receiver with these sort of speakers.
Ofcourse, if you plan on upgrading the speakers soon anyway, then this will be a good investment that will work better with the new speakers when you choose to get some. But in terms of most bang for buck, right now with your budget, I'd look at getting solid front and center speakers. Bose speakers are very easy to sell and you'll probably make up the money you got them for in the first place since you say you got them cheap.
One suggestion is to retain 2 161's for surround duties and change the LCR where most of the stuff happens anyway. Even budget bookshelf speakers will give you much more bang for buck with your budget. For 300$ you can get a very good receiver with auto calibration and you'll end up with a much better system for the same money.
Two examples from the top of my head are PSB alphas which go for around 200$ a pair, and the Wharfedale Diamonds which go for even less. Matching centers shouldnt cost more than 100$.