lets think it through slowly.
wired (UTP) - either 10Mbps or 100 Mbps
wired (BNC) - 10Mbps
wireless - 11 Mbps
not much speed difference between wired or wireless, unless u invested in Fast ethernet. And this speed only refers to the devices(router, PCs, ...) within your home network. Anyway, the pros and cons between wired/wireless is not in the speed. Its in security, guess which one is easier to wiretap??
Your internet connection, as you said, only 512Kbps, is a fraction of 11Mbps, where do u think the bottleneck is?? at the slowest link right?? For sure, your home network (LAN) speed will always be faster than your internet access. so really no need to pull your hair out worrying so much about the speed to choose.
Basically u are asking the wrong questions. its like people asking about number of megapixels on the digial cameras, when we all know the image quality is in the CCD technology, not in the number of megapixels. Give u 5 or 6 MP but lousy colours, the pic still sucks.
As someone has pointed out, make sure the wireless AP/router supports standards, where all your hardware can inter-operate. For now, make sure it has security features, which means WEP until something better come along.
And, the most important thing, the router is reliable. I know some broadband router reboots every so often. Or some wireless AP stops operating after some time and need to be rebooted. Trust me, these things are way more important/frustrating than speed.
netgear, linksys, dlink are mostly reliable. sometimes certain models will have problem, but are usually fixed with new firmware upgrades.