In no particular order....
Different Finishes would be great. Being able to integrate audio equipment into a room's decor is getting to be extremely important as high style products, like plasma TV's for example, become more common place in the home. Piano Black is nice, a brushed aluminum would be sharp, and there are obviously many many different veneer variations out there to make your products unique. Real wood is nice, but veneer will keep everyone’s costs down.
MISC: If I didn't see this on your website please add "website update" as one of my choices, but I'd like to see some quality (QUALITY being the key word) in wall subs like dual 8" or a nice 10" with a passive radiator to mate with your 500 watt amp. I could see a great deal of applications for being able to hook up two in wall subs to that amp and then mounting the amp in a rack.
Slimmer profile subs could be marketable for the reasons mentioned above in explaining the different finishes. But, I would take the slimmer piece a bit further or different and make something like a sub with down firing dual 8” drivers. When done right, the products I have heard configured like that are great with music. It would be a unique and different piece to offer.
Also, dual driver products (slim profile or not) could really step your offering up a notch. Dual 10’s, 8’s, or 12’s can really kick people in the rear. To me, a sub should be the most expensive speaker in a home theater. Don’t be shy about offering some higher tiered products above the $1K mark. There’s a market out there for it!