The Cinemar's products you mentioned in the title will do control of a DVD and music server. Music Lobby uses MC as the "guts" for the music portion, but they use their own client server module (DVD Lobby) for DVD management. I use ZoomPlayer instead of Theatertek for PC DVD playback via DVD Lobby, but they are pretty similar (although in hindsight, would have gone with TheaterTek).
I have all of the Cinemar products with the exception of the Music Lobby Pocket PC version which came out after I bought my setup. I did get the DVD Lobby Pocket PC module, but have yet to get it all installed and working on my Pocket PC, mainly due to lack of time on my end. I have an iPAQ 2215, which is a great unit but it does not come with WiFi built in (can add via CF slot). Thus, that is a drawback if you are shooting for a client/server setup with the unit in an all in one package. The newer iPAQ model comes with WiFi and Bluetooth built in.
I did buy a Compact Flash WiFi Card for the 2215, but there has been a lot of problems with non-existent or beta only drivers for many cards that are used for the newer Pocket PC 2003 OS (namely the Linksys WiFi card). One advantage with the 2215 is it comes with the higher power IR unit for remote control of IR units, but you are more interested in client server technology, which will require a Ethernet connection through a WiFi card.
I have found that battery power is the main limitation to the Pocket PC setup, especially with WiFi Card active (which you have to, if using client/server setup like MusicLobby). I was looking more for a remote control setup that I wouldn't have to worry about constantly putting back in the cradle for power. At least for my 2215, I was only getting a couple hours with WiFi working. On the Cinemar forums and the AVS Forum, there has been lots of talk about using the PC tablets, such as the Airpanel. You can also probably get more first hand experience from people who have gone the Pocket PC route on those forums. From what I have seen, it seems that the tablet approach is a better solution if you are trying to do the "most coolest remote" thing by using it to control a music and DVD server setup, along with IR blasters to control your IR equipment. Tablets have the advantage of bigger screen and touch screen ability.
If you go the client/server setup, plan on lots of fiddling time. It takes awhile to get everything working correctly. MusicLobby, MC, DVD Lobby, TheaterTek, IR receiver, Pocket PC, Girder (if using to control IR from PC), Main Lobby (the client/server module), etc..etc. I consider myself a gear head, but it was getting a bit overwhelming, especially (in my opinion), since the documentation on the Cinemar products leaves a lot to be desired. Plan on spending time in their forum and lots of trial and error. When it is all working though, it is great.
For me, I am sticking with my MX-500 and MX-800 remotes to control the Cinemar products for the moment, until I get time to play more with DVD Lobby Pocket PC and see how that goes.