What speakers are you driving with that 705? Impedance, sensitivity, listening distance, normal listening volume, all has an impact as you may not need an external amp at all.
Mtrycrafts has asked the most important questions of your decision.
If you do decide to go with seperates, with your budget, I would recommend going the prosound route. I like Crown amps, lots of members here like the Behringer amps, QSC is also great. Behringers Europower and Crowns XLS series are both within your budget for powering your mains, but a few things to keep in mind:
1) You need to answer Mtrycrafts questions before even considering seperates
2) Pro-amps have fans for convection cooling which make some noise. WmAx has replaced fans with quieter ones, maybe you can search for something on that or just call the company you buy from and see if they have a recommendation.
3) Careful with the gain knob.
Behringer 1500s are two channel amps that make 260watt at 8-ohms. 300 bucks on B&H, but you can find them *much* cheaper. Two of these could power your front three, with a channel to spare.
Crown XLS402s make 300 watts per channel at 8ohms for about 400 bucks, but you can also find them cheaper also (and they have a 60 dollar rebate going on them now). Crown also makes a XLS202 that makes 200 watts per channel at 8-ohms for under 300.
Just food for thought.