Peter
How much do you want to spend and how complex a solution do you want?
I think the challenge is the AAC part, you pretty much have to stick w/ Apple-related equipment.
1) Apple TV. Possible solution but you need component or HDMI input on your TV. It needs your PC/Mac to be on but the ease of use is there w/ iTunes and AAC support. $300 or so.
2) Squeezebox and Roku are also good but I believe those also need a PC running.
3) Sonos is nice but a little pricey IMHO. Easy to use, wireless and lots of function though.
4) HTPC can still be useable w/o an HDTV. If you set up with a VNC client, you can use another computer, like a laptop to control it w/o actually have a screen connected. I use a Mac Mini in my HT to serve up iTunes/music and I control it this way with Apple Remote Desktop. I almost never use the plasma which it is connected to. This is doable on PC's too.
5) Yeah, Tivo is also a good solution. I have a Series 2 and 3 and it's cool to serve music and photos. Granted you have to pay for tivo service too. Here's a thought, maybe you can get a used S2 and hack it w/ PTVNet to enable the music serving but not use it for Tivo, which you then wouldn't have to pay for? But it doesn't solve the AAC problem.
6) I think you're best bet is to go w/ a simple iPod dock like this:
iPod AV Dock This can connect to any receiver, so you don't need to upgrade to an iPod-specific one. Any of your iPods can connect to it (and charge) and if you have video, it'll work for that too. Also, it comes w/ a remote. If you're so inclined, you could even set it up to work w/ a universal remote like a Harmony or Home Theatre Master.
