robricc, very nice to hear that you are pleased with the AT; I just ordered one as a matter of fact. The RIO was nice, but after I settled in my new house and really hooked it up to seriously use it...the display on it (RIO) was absolutely unbearable. Where I had it before in my bedroom it was no more than 6 feet away...now..in my living room I decided I needed a more readable display as the RIO is about 12 feet from the couch.

Now...to get back on topic :-)

I have never used the RIO with the server software it comes with. My Linux server has all of my MP3's so I just used JReceiver on it. I struggled for a while to get the Broadcom HPNA drivers to work (thanks everyone here for the help and links) but was unsuccessful. They are not fully open source (stub binary with source to hook it to your kernel). New house is now wired with ethernet :-) With JReceiver you can have a catalog of MP3's of basically any size...it uses a MySQL database for holding your MP3 info. As far as resources used, JReceiver uses quite a lot of RAM via it's JAVA interfaces with Jetty, but it really takes almost no CPU resources on my P2 450 to serve the MP3's. JReceiver seems to be pretty polished for an alpha release and works very well with my large MP3 catalog. As for gaps between songs....well...you do get slight gaps.

Rio pro's in my opinion:
Extremely inexpensive.
Heavy 3rd party support (some nice full client software replacement packages available).
Easy to fit in just about any small area.
Built in amp is real nice for when you place the RIO in a bedroom and don't want to use a whole stereo system....sounds good and is quite loud to boot :-)
Fairly clean DAC as opposed to what I have heard about the AT.
Direct shoutcast streams using RioPlay without having to depend on, for example, Turtle Radio....which could at some point in time become no longer supported.

Rio Cons:
Default client software sounds terrible compared to RioPlay with Libmad. Replace this immediately :-)
Unreadable front display, almost makes you wonder what the remote control is needed for.
Doesn't blend in with rack sized stereo equipment.
Future updates from Sonic Blue just ain't gonna' happen.

Also, the AT is starting to see 3rd party support as in: http://www.deepskytech.com/prod_appls/alternatron/
It is also unofficially condoned by the Turtle Beach as is somewhat apparent in their support forums for the AT.

All in all the RIO is a nice little unit that does what it claims to do. It basically comes down to how/where you are going to be using it. In a bedroom or dorm room where it is close by and you don't want a stereo system....I would go for the RIO. If it is going to be intergrated into your home stereo/theater system...I would go for the AT with a digital out to your stereo to avoid the rumored bad DAC. As far as PC requirements...at least for me...indexing the MP3's to the database takes CPU and RAM....but streaming them to the RIO takes almost nothing in resources. Won't even notice it's there.

Oh jeez...did I ramble on enough yet?? What was the topic again?........*sigh*