I've not heard the HTM-10's. There are a number of threads on other forums that go into detail about the DIYSG speakers and their designers seem well spoken and diligent. There are many folks that have built them that like them.

Thing is, you already have the 2226h woofers. These aren't the entry level woofers for the 4 pi's but the full blown upgrade woofer. They are also the single most expensive part in the 4 pi build - about $1000 for a brand new pair. It's a great woofer even when you have to buy them retail but you already have them ... IMHO it'd kinda be a shame to ignore them.

My $0.02.