I have no direct experience with the subwoofer you specified. I do have some fairly extensive experience with Kenwood as a whole, however.
Most of Kenwood's entry-level subs are just that. Entry-level. Some decent cosmetics but for the money there are better products to be had elsewhere. I've run Kenwood amps for years and years and have never had a single one of them give me any problem. Keep in mind, though, that the only recent Kenwood amps I have run have been eXcelons (my 4-channel being a Performance Standard from before the eXcelon amplifiers were labeled as such) but the various "regular Kenwood" 2-channel and 4-channel amps I have had from older model years have given me flawless performance.
Kenwoods coaxials, component sets, and add-on tweeters haven't been particularly up to snuff (IMO) in recent years either. It's not that they are bad speakers but they aren't the speakers that their price points would suggest that they should be.
On the other hand, Kenwood's eXcelon subs, in my experience, have been pretty good - especially if you can find a good deal on 'em (like buying them from
eBay once the next year model has come out and distribution centers just want the old stuff GONE)
There are other shallow-mount subs available (specific models escape me at the moment) that I really feel would serve your brother better.