I have given up looking around for a 4425 to use as a center to go with my 4430's in my HT. They are rare here in Canada. I have a couple of 175DLH's kicking around so just for fun, I ordered a .75 cu.ft. cabinet from Parts Express (these cabinets are really nice - 1" thick baffle!) and a pair of Dayton aluminum coned 6" woofers.
So, this weekend, I put it all together. 175DLH in the middle flanked by the two 6" Daytons. It only took a few hours including wiring up a simple first order H/P crossover at about 2500 Hz and a pad. So far, I haven't added a L/P xover, for now I'm just letting the woofers roll-off naturally.
First hooked it up to my two channel he-man rig in the basement - very impressive, albeit in mono. Then I went upstairs and installed it above my 42" Panasonic Plasma, what a difference compared to the crappy little speaker I was using before! Looks cool too and compliments the 4430's visually.
Short term listening last night revealed how important the center speaker is for surround. A real eye (ear?) opener. The conical dispersion seems to work just fine with the buttcheeks. This is definitely a keeper.