Need more info, but first impressions are...meh....
Dollar for dollar, the Monoprice subs don't look like anything special against what ID subwoofer vendors are delivering these days. A Monoprice 10"/500W/$500 or 12"/500W/$800 ported subs vs the Hsu VTF2.5 and VTF3.5 respectively? No thanks. As for the 15", it'll have its work cut out trying to compete against the FV15HP and V1801.
And of course beyond price vs performance, there are those little details like support. Historically when I've pinged SVS, PSA, JTR, Funk, etc., I'm talking to people like Ed Mullen, Tom Vodhandel, Jeff Permanian, and Nathan Funk. I can't say I'd expect a similar level of attention from a company mostly known for selling bulk cable at low low prices.
PS:
This guy from last year looked a lot more interesting, even if it was vaporware with bullshit specs.