I also am in my basement. I usually get between -68 to -70 signal. My drawback is traffic. Which can not be helped.
Sounds like many will spend on amps, I almost made the same mistake. I have the yagi on a steel water pipe pole stuck in the ground. Sucker was 20' long. So I just drove it beside the house standing on the roof with a fence post driver. (or T-post driver). I also have the truckers beside it too. I switch back and forth for fun, I think the yagi draws better though.