Payoffs Plus aka BetPop is rated "C+" by Sportsbook Review.
they advertise a "70% Sign Up Bonus" but it can't obviously be a straight cash deal. no specifications for the bonus terms, maximum bonus amount or rollover are listed on the site (at least at first glance) which can sometimes be a red flag, but SBR hasn't reported anything shady so far. I guess check with customer support for more details.
here are the parlay charts. 2 and 3 team payoffs are pretty good but then it seems to go downhill.
http://www.betpop.com/payoffs.php
overall the place looks to be a bit low budget. their claims of being a "Discount Sports Book" like Charles Schwab are a bit over the top. also if you click on the Live Chat link, it takes you to a page "AVAILABLE SOON".