Routers with QoS (gaming routers): any good?

It really all depends. If you're already making use of all the available bandwith for your downloads, then switching to one of them "gaming routers" probably won't do much. But if you ARE limiting your torrents already, then depending on what actual algorithm is used to limit your torrents, it might be possible to get better performances. If whatever client you use limits bandwith by sending or receiving the maximum amount of bits it can in a burst every second, instead of spreading data transfers over the whole second or whatever period it uses, then it's likely that your online gaming could be improved by a better load limiting algorithm, which your router could provide. On the other hand, if your client is already trying to make sure it does not send or receive data in bursts, a gaming router would do shit for you; the only solution would be to limit the bandwith allocated to torrents even further.

Of course, this assumes you can figure out just how your torrent client handles load restrictions. Don't count on it.

Jam it back in, in the dark.