Are you using a router right now? Here's what I recommend: get a good, quality router. I just switched to a Netgear N600 (WDNR3700v2) and the improvements in streaming video quality over WiFi was dramatic.
I bought my parents a WDTV2 for Xmas, and they love it. I was very surprised when I found out that it played VUDU HDX movies wireless without any issues. So, it might be your ISP as well. Vudu has a testing utility and it will tell you the best video you'll be able to play with whatever internet connection you've got.
Media Server: UnRaid Server: 15TB of storage and growing :).