I run a 2.6Ghz farm. Phoenix is my miner of choice due to stability. I have tried Trex but frequent crashes left me with too many outages. I haven't used GMiner so I can't speak to the efficacy of their software.
Try to use it. Gminer is the best miner as for me. The most stable and gives the best hashrate. Phoenix gives less hash then T-rex and Gminer. And if T-rex have some problems with stability, Gminer - have no problems.