KW T660 aftermarket headlights

Are you sure? Tried the website ?
http://www.jwspeaker.com/products/categories/headlights/
Mine are 7" round so obviously different to yours, but if you can get them I highly recommend.

 

I'd like to see an example of anything that would be cheaper at a KW dealer than elsewhere LOL. On my T600, stock front turn signal bezels (bulb type) were $155 each at KW. LED from 4 States were $55 each. The good news is, you don't have to buy them at Caterpillar.

OP: Google is your friend. Plenty of aftermarket options to go with, apparently in the $300 a side range. I bought some complete units like these for an older Century for $325 a side, so these are priced about the same. The ones for the Century were a bargain compared to going in with stock parts, which would have added up to around $600 a side from Freightliner. I wouldn't waste too much time worrying over how long they last or get hazy. They will all eventually get that way or catch a rock. Usually by the time that happens, changing them out is due anyway. The plastic mounts and hardware just won't hold up to the abuse all that well, no matter where you buy them.

 

I only changed out that Century, so not much to share. The fit was ok, more issues with the million+ miles hood to get the holes to line up on one (cracked) side, not really the fault of the headlight module. The other thing was, since the OEM setup was old style lamps with sockets accessed by pulling lamps out from the front, the new ones being H7 that you get at from the back. I had to plan ahead and make some access holes in the fiberglass behind the lights to get at the sockets for future replacements. Otherwise you have to pull the whole module out to get at them. It'll be details like that probably, before you struggle with fit.