Ive never heard of Pool-x.

Ive mined with MT.red, BTC Guild, 50 BTC...

IMO 50BTC is by far the best in terms of ease when connecting your miner to a pool, high-tech website plus there Fee's are very reasonable.

Here is a Link http://thebitcoinminingoutlet.com/?page_id=1284 to a Step-By-Step guide to configuring a Miner to the 50btc pool.

BTCFTW!