Hey James,
Funny meeting you here.
I'be been switching over to Logic more and more from DP for a few reasons. One is the CPU friendlyness if it... I can run a lot more plug-ins at once. The other is that it comes with some great synths and plug-ins... and their pre-sets (including a bunch of channel strip presets) are very useful.
While this doesn't seem to be answering your question, I bring it up because Linux might not be as compatible with a number of plug-ins. I did some play with an older box with Linux, but I stopped short of really digging into it. I imagine there's been some huge strides since then, and I'm really not an expert when it comes to making music on them. I just thought I'd speculate with you....
So while you might be saving some money on the OS and computer rig, you might be paying more to get those plug-ins and synths to make it sound and act as pro as Logic does out of the box. Having a full selection of audio interfaces might be an issue too.... or the drivers might be buggier than those written for Mac/PC.
The studio space issue with a Mac is the same as a Linux...
What some people are successful at (not necessarily me) is to get your rig working like you want it to and then leave it alone for a couple of years. Having the philosophy that it's your instrument rather than your computer I guess... Sure we water at the mouth when we see that new upgrade, but if forking out the cash to get the latest greatest thing is an issue, then you might not need to upgrade at all. I know one guy who does great synthestration work has an old G4 tower still. (plus Giga)
A lot of the sample libraries comming out now in virtual instrument form are still based on the older libraries written for Giga. And those older Giga libraries are getting cheaper now too.
I'd love to hear if you go the Linux route. Again I'm not an expert... probably just like to hear myself talk (type?).
Best of luck,
Richard