These are value for money speakers. I heard them at Hi-Fi Lounge, Alabang demoed with Cayin tube amp and tube cdp. They sound good in audio even if they are actually intended for HT. Good all rounder for budget HT/audio set-up. They look good too; they look more expensive than their actual price.
If I were to pick bet F6600 and the F5508, I will go for the F5508, just for a little added bass. Besides that, these two sounded they same to me.
I think they are not biwirable. The center F5500 that I bought is not biwirable. In fact the binding posts are smaller than most, and I had to really squeeze tight the 12ga wire that I used with it.
The prices in the above post are still the current prices. Just bought my center last Dec 4. These entry level speakers are real value for money.
But if you have 25K budget, and you're only intending to use it for pure audio, I believe there are other alternatives out there that you should also consider
(wont mention them here since this is AC thread ;just visit the other speaker threads). Just try to audition all the alternatives, so will be more definite in your final choice.
They have speakers for audio, but I think they are already beyond the 25K mark, like the Voila that I also saw at Hi-Fi Lounge.