Thanks, alfaz12.  You were asking about a GPU for a tower unit, alfaz12.  AMD's 5970, 6990,  7950, 7970  and 7990 all seem to be popular cards.  I seem to hear a lot of people talking about the 7950 and 7970 in particular.  Their individual wattages and estimated kh/s are on the Litecoin hardware comparison site at https://litecoin.info/Mining_hardware_comparison .

I don't really know anything about mining on an android device but I don't think you'll get much of a hashrate.  All I can advise on that is to maybe check out the reviews at Google's Play Store https://play.google.com/store/search?q=litecoin%20miner&hl=en_GB 

With all the pool mining software I'm aware of you don't need to keep your Infinitecoin wallet open during mining.  You can just shut it down if you like.  Then when you choose to reopen it, any Infinitecoins that you've earned in the pool will show as the wallet gets itself up-to-date with downloading the blocks .