I use Verizon FIOS and I generally get between 12-15Mbps, with two PCs connected. Depending on throttling and high volume in my area, It's hit or miss with streaming for me, too. Generally, 95% of the time I can stream with limited buffering ( if any) but that 5% is annoying. I'm not an expert by any means, but with my experience anywhere in the teens should be fine. If you clear your cache and all those little tech tricks, the 5% isn't as frequent.
Probably doesn't answer your question, but know you're not the only one with this issue.