Mastering a full album in Sonar: average RMS?

I used to do CD compilations in my audio editor, import all the finished (mastered) songs into one track in sequence.
Perceived volume is determined by average levels rather than peaks. The easiest way to measure that is Average RMS and start from a couple of reference levels, one for fast tracks and one for ballads.
Sonar has progressed in its mastering capability in its latest versions and expansions and I am about to master a full album in a sonar X1 session. Is it possible to get the average RMS out of a stereo clip within Sonar or with a suitable free utility? I don't mean realtime plugins.
If not, I would go to the audio editor only for that, but that would be time consuming (sonar bouncing and exporting, opening editor, measuring and listening, then go back to sonar and adjust threshold in the limiter).

I understand that average RMS is not all, but it's a good starting point, and really needed to do this job.
To clarify and share: if the compilation CD comes from songs made in sonar, and I have the original mix sonar sessions, when I increase level through limiter threshold I check by ear:
a) are dynamics squashed? (a drum fill-in, a paused middle-8..)
b) is clarity and instrument definition compromised?
c) is bass and drums presence changed and overwhelming over other instruments?
b) is main voice level balance against other instruments increased and different from the previous song?
c) are there new sibilances in high freq?
So I really understand that listening properly is essential after raising volume, and it's really useful to have chance to get back to the mix in these modern times and apply limiting there (and compression along the way from the instrument track to the bus and to the main bus, that's why I like X1 prochannel).
But, to start with, I need measuring the average RMS of a clip (a stereo master export).
I'm currently checking how to force sonar meters to get a very slow RMS..
If not, I will open a feature request, since it would be very simple for cakewalk to add this. Would you support it?

I have exactly that need right now, to hear and fine-tune all songs for a CD production, next to each other.

There are tools for that (WaveLab?), but the Concrete Limiter settings for each song's Master bus also need adjusting per song, and since that is not a VST, I find myself up the proverbial without a paddle.

  I use Sound forge for mastering for that 1 reason... Statistics. In Sound forge you highlight all or even some of a song and hit the statistics button in the tool menu and instantly know the RMS. It's easy to process the mastering chain, check RMS, undo the mastering, pull the threshold up or down in L2 and re-check stats till the song is hitting a good RMS. It's a great starting point with superb accuracy. I wish Sonar had instant stats on RMS/Peak. I don't mean while it's playing. The whole song's RMS right now.

I like the TRacks metering. It gives you percieved loudness as well as RMS. There are settings for suggestions for different styles as well.

Generally for dynamic songs I'll check the RMS of the Loudest section of the song and go from that point. Again these are starting points. Like bitflipper said RMS values change constantly. Ears are the final judge. I've got SPAN somewhere, I'll have to check the mastering mode. Sound forge has been great, but I haven't upgraded it in while and it doesn't see my new 64 bit Waves plug-ins. (Yaay for waves! No ilok for them now either... jump drive instead. 3 keys instead of 2 eliscense, iLok, and jump drive)

Since you have Audition, use it to measure average RMS over the bulk of the song, excluding fade-ins and fade-outs. That's just one measurement and can be misleading taken alone, so also select the loudest and quietest portions of the song and see what the RMS is for those sections, and the difference between them. This will tell you if the loudest parts are overcompressed, and whether reducing overall limiting is a suitable cure for it, or if you'll have to fix it in the mix.

Of the statistics Audition offers, the histogram is probably the most revealing. The distribution you want to see depends on genre and style. For me, I'm looking for a nice wide bell curve that's highest around my target RMS for the song. I'm also on the lookout for anomalies that might indicate a few rogue hits that could cause audible breathing.