There are a number of things you can do with the GT-101 that you might not have thought about. This page lists the extended applications of the GT-101.
The GT-101 is sufficiently sensitive that you can drive it to full output with an Ipod. All you need is a Stereo 1/8" male to dual-male RCA cord. Radio Shack carries 3 foot and 6-foot versions of the cable. Just plug the RCA ends into your GT-101 and the 1/8" end into your Ipod.
I use a GT-101 with a dedicated connection to my CD player. There's just less to get in the way of the sound. My CD player doesn't have a volume control. I added one to my GT-101. The volume control is optional. It requires that you drill a hole in the chassis. Here are the Assembly Instructions for the VC101 Volume Control Kit. Here's where you can Order the Volume Control Kit.
The GT-101 is unique among amplifier designs in its use of an electronically regulated power supply. That changes some of the usual assumptions about power supply behavior. Still, you can make your GT-101 put out even more low frequency power if you change C6 from 4700 uF to 10,000 uF. Here's where you can order the 10,000 uF upgrade.
Please note that it is best to do this when you order the kit. It can be done as a retro-fit, but please send me email asking for special directions.
Do you want to add some signal processing to the GT-101 that isn't already built in? That usually requires the addition of a low voltage power supply, but the only power supply in the GT-101 is a high voltage unipolar supply. What if you wanted balanced voltages of around plus and minus 12 Volts? How could you get it?
Well, you could add another transformer, or you could add some turns to the existing power transformer. Adding 40 turns of magnet wire to the existing toroid would give you a 12 Volt RMS winding. Add a couple of diodes and caps, and you can have a +/-12 Volt supply to run low level signal processing circuits.
Cruising the web, I found Audioengine's Wireless Audio Dongles. Looks like a nice way to wander around with a laptop, yet still get great sounding music through your GT-101 and serious speakers.