The most RAM usage (per the Sonar indicator in the Performance Toolbar) has always been less than 2 gigs (!!!), and that is based on over 200 multitrack sessions with softsynths and multiple plugins running.  Is that because I am still on 32bit XP?  So is anyone seeing a lot of RAM being used, and what are you doing to use that much?  Also, please indicate what OS you are using.  Thanks.
 
PS:  I've participated in several posts where other forum-ers have claimed that they say performance improvements due to lotsa RAM.  I never questioned that.  Now I did recently run out of CPU, and had to overclock the thing to get by ... so it seems that maybe you'd be better off spending the RAM $$'s on a faster CPU.  CPU more important than RAM. 

Without knowing the specs of your computer, there is no way to help you.
 
XP has a limit of 4gb of ram. While this is sufficient, it also depends on your CPU. If you have to overclock your CPU because you need better performance, my guess is you have an older computer. Again, we can't help without knowing your specs.

I don't need any help, thanks, other than perhaps mentally ... I just wanted to see if and under what circumstances Sonar would be using a bunch of RAM.
 
As to my computer it is a year old, Athlon II 945 quad core overclocked to 3600 with Adata gaming series DDR3 running at 800 with 9-9-9-24 timing.  The reason I overclocked is because I ran out of CPU, not RAM.  Only 1.7 gigs of RAM were being used (which includes the XP OS) in a project with 5 softsynths, 4 guitar tracks with compressor, Session Drummer 3 track with verb, 13 vocal/harmony tracks with compression and v-vocal running on some clips all routed to a vocal sub-out with vx64 vocal strip doing its thing, 2 bass tracks (one tube overdriven) compressed, hi-pass filters on all tracks except kick and bass, all running through a mastering plugin on the master bus.  All tracks stereo.   With the CPU running at stock 3000, I had the pops.  I don't like pops.  Only one other project that I did 3 years ago did I have the rice krispies going on, and that was on a dual core cpu.
 
I see what it takes to run out of CPU.  What does it take to run out of RAM?

A Windows OS system never "runs out "of RAM. It is designed to always map out a portion of the hard disk drive to use as "stick RAM". This is called 'The Swap File'. This swap file is 'laid out' to behave as actual stick RAM modules and all programs sees it and uses it in that manner.
The main drawback is that, it is slow (can be thousands times slower). Imagine sending a messenger to a warehouse (data) 10 miles away. Stick RAM is like using a car--Swap File is like using a bicycle. The more Stick RAM you have, is like having a whole lot more cars for courier.

I tend to agree with the OP. Given the choice, money in a good CPU is better than more RAM. Plus, RAM can be upgraded more easily (if needed). I have rarely run > 4GB in use on this machine doing audio functions, and it renders 5.1 surround sound files out of Audition at ~50MB/sec. Even when rendering video, the CPU is the chokepoint on this, so I have never felt constrained by RAM.

You can't compare the use of ram on a 32bit OS and CPU performance.

Once you move to a 64bit OS it opens up completely different possibilities for software, not only in how much ram you need but how CPU performance changes.

Timeking
The most RAM usage (per the Sonar indicator in the Performance Toolbar) has always been less than 2 gigs...

32-bit Sonar uses a maximum of 2GB RAM.  Earlier versions (e.g. v6) used to crash if it went over the limit.

my pagefile is static 512 megs, so whatever ram needs are not being supplied by the pagefile.  Also, if 32 bit Sonar only uses 2 gigs of ram, why don't I ever experience some sort of random crash or inability to load yet another plugin? 

Timeking
...if 32 bit Sonar only uses 2 gigs of ram, why don't I ever experience some sort of random crash or inability to load yet another plugin?

Most plugins themselves don't need much RAM.  It's the sample content used by certain softsynths that makes the difference.  Try adding lots of instances of DimPro to a project and loading up each element with large samples.

We've become accustomed to what is a literally unimaginable amount of RAM. Think about it: a gigabyte is 8 BILLION tiny switches. It boggles the mind. The first computer I programmed had 4 KILObytes of RAM, and I managed to write video games with it. 10 years later I was working on systems that ran entire companies with hundreds of users, on 8 MB. My company's high-end box was a couple million dollars and supported a maximum of 128MB. Later on I was coding on Sun SPARCstations, which offered an unbelievable 16MB - on a desktop! The Space Shuttle was designed on computers like that.
 
Increases in available RAM have made programmers lazy. No longer do they carefully allocate exactly how much memory is needed and dutifully return it to the pool immediately after it's no longer needed. As RAM increases, so does the need for RAM. But it's still possible to write useful software that runs in a few hundred kilobytes just fine. SONAR is one such program, having its roots in a time when far less than a gigabyte was the norm. Load up an empty project and note the RAM usage - it's pretty small.
 
Then start adding plugins and watch the memory usage rise. Most effect plugins add so little as to barely make a blip. Start recording some audio. Again, memory usage rises very little per track. Overall system memory increases as Windows attempts to buffer all that audio data, but that's in the disk cache and most doesn't come out of SONAR's share. You can in fact have a huge all-audio project and easily remain within SONAR's 2GB limit.
 
The big RAM-gobblers are sample libraries. My largest one wants over 3GB, but Kontakt also has its roots in times where 1 or 2 GB was all the machine had, and uses memory frugally. I routinely have a dozen or so sampled instruments loaded under XP without exhausting RAM. However, those libraries are carefully chosen for efficiency (one of the reasons SampleTank 2.5 is still a favorite). If I could afford to, I'd happily replace my aged DAW and O/S and load that sucker up with as much RAM as it'd hold. In the meantime, I practice stingy memory management and freeze a lot.
 
And the funny thing is my technological restrictions do not creatively stifle me in any way. If anything, the opposite is true: the emphasis shifts from what cool sounds I can layer on to the music itself.
 
At the moment I am exiled, not only from recording but from even strumming a guitar, leaving me with only an MP3 player full of gigabytes of other peoples' music. I've been listening a lot and marveling at what can be done with a guitar and a piano.
 
To the OP: yes, you have about a gigabyte and a half to play with, period. Fill it with music.