I right now have a setup which gets me my CPU, MB, Ram and PSU all for $240, all enough to power 8 GPUs
Is this a good rate for the supporting system?
Price wise Yes, however the question really is How reliable your cheap hardware? did you purchase those cheap brands or chinese products unbranded or cloned ones. mining is a 24/7 workhorse, the most pressured hardware will be your PSU and GPU's. so better choose a decent one for this two.