What do you use to keep high gloss speakers clean?

Bowling balls you smut merchant LOL 

The Meguirars is quite good.  Pledge, which I also use on my racing car, is easiest.  Pure carnuba airplane wax if your speakers are exposed to UV light from a window.  Zaino wax gives the deepest breathtaking 3D liquid-like gloss I have ever seen, but takes a great deal of time to apply to a vehicle.  It might be worth it for furniture having a smaller size as you mention. 

Seriously suggest you take a look at Zaino Z5 Pro Show Car polish. It is a polish and polymer sealant. I use it on my gloss black B&W 804 D3's and touch up with Zaino Z8 Grand Finale. Normal waxes like Meguiars  will evaporate in about 30 day. The Z5 has to be used in conjunction with the Zaio (like a catalyst) but I can assure you, it is superb. Check out the reviews. Also, to substantiate the comments by IBMJUNKMAN, I never use any cloth with any stiching at all. Zaino is the only place I know of who make "border free" towels. These are what I use on my car also. Micro fiber cloths will definitely create swirl marks.

Tried most of the choices above. The Meguires quick detailer and Plexus seem to work the best. IMO.

+1 on the Gerlitz it's amazing stuff!