Try to get one with a RK3188. It runs the RK3188 which is the quad core version of the RK3066 and these days they are only around R200 more expensive. If you can, get one with an external antenna. I just missed a great deal on one here:
http://www.bidorbuy.co.za/item/129669924/Mini_Quad_core_rk3188_cortex_A9_android_4_2_tv_box .html
Try and get one that has a following on forums like Freaktab so that you have a support base for questions or problems.
I have one of these, R1200 delivered from a reputable seller on eBay:
http://www.geekbuying.com/item/NEO-...8-2G-16G-BT-External-wifi-antenna-317282.html
There were some VSYNC problems initially (jerkiness when playing any video) but I found a kernel on the Freaktab forum with comprehensive instructions on how to flash it that fixed the problem. The jerkyness is a problem on all Rockchip players unfortunately. XBMC also launched a Minix-specific version of their software in December 2013. I can honestly say it is fantastic. Rock stable, snappy, customizable and tons of support.
I gave my brother my old Tronsmart when he moved into his own place and although the WiFi was not excellent, it was not much worse than my phone. Nice review of that one here
[video=youtube;_B7ALe7qTSQ]http://www.youtube.com/watch?v=_B7ALe7qTSQ[/video]