As per usual, ignore the RRP but this as a decent deal for a Sub of this calibre in my opinion. It's designed for PA use so it wont be as accuate or extend down as low as a Hifi Sub however it's built tough and is designed to handle the abuse of PA applications (Schools, Churches, Clubs, Cafes, Bands, Mobile DJs etc.) specifically for filling larger rooms or even small outside areas with lower frequencies. You could still easily use it for home audio too (ie. crazy parties) and it should last longer than using your nice Hifi gear and it will still sound amazing but can't reproduce those stupidly low freqs as well. An all-round decent little entry level PA or DJ type Sub that wont break the bank. Oh, and the 250W rating is its RMS value.
If the quality of the Wharfedale Titan 15" sub is anything to go by, this one will be amazing too :) I've got two 15's and I've never maxed them out because they're just too loud, and this is coming from a bass enthusiast :)