Looking for opinions about PC upgrade

I bought the most basic version of Sonar several years ago when I was thinking about trying to use it with a Mackie firewire mixer to do 8- or 16- channel live recording.  I gave up on that idea for several reasons, not the least of which was that my notebook computer was too lightweight for reliable operation.  I think there are better, easier, more reliable ways to capture live recordings.
 
So that software sat on the shelf.  But recently I decided to upgrade, and I now have X2 Producer running on my desktop PC.  My main usage in the next 6 months will be to master some live recordings, and it is working out very nicely for that.  And along the way, I am learning about using the DAW for composition.  Because my current hardware is more-or-less doing the job, I don't think I really want to do a complete hardware replacement today.  I think I will have a better idea what I really need in 6 months.
 
HOWEVER, there are a couple of issues.  I occasionally get the dropout problem.  Most of my recordings are just stereo or 4-track, and that usually runs without dropouts.  However, when I tried to play the demo song that comes with X2 (a whole bunch of audio tracks) I could only go about 1 measure before getting dropouts.  So I can see that my system won't take me too far up the power curve.
 
I can live with that at the moment.  However, I am using the sound card function that is build onto my motherboard, and it is limited to 24-bit, 44.1KHz.  I have a Presonus audio interface that will do 96KHz, but because of that on-board sound processor, Sonar is forcing me down to the lowest common denominator.  My recordings are originally 96 KHz, so I'd like to be able to keep that same precision when mastering in Sonar.
 
Just for reference, my system has an AMD Athlon dual core at 2.7 GHz.  I am running Windows 7 and have 6 GB of RAM installed.  The motherboard is probably 3 or 4 years old, so the backplane isn't nearly as fast as today's systems.  I think the memory is DDR2.  I am running the 64-bit version of Producer.
 
I imagine I will eventually get a current motherboard and a system with 4-to-8 cores, and probably run everything from the fastest SSD drive I can afford.  But that's some serious money.  I am thinking I can solve the 44.1KHz limitation by installing a Soundblaster Z card and disabling the sound function on my motherboard.  That Soundblaster will do 96KHz.  That's about $100.
 
Does this seem like a sensible plan?  Any other ideas?

Thanks for that.  That's the kind of thing I was looking for.  But by "bypass the internal sound card altogether" do you mean actually disabling it at the BIOS level?  I don't think I can do that on this system because it is shared use.  I am not ready to dedicate a system entirely to Sonar.  I use Finale and Band In A Box on this machine, and I think they both require a regular PC sound card.  I may be wrong about that.
 
Or are you saying that I should disable the internal sound card with a setting inside Sonar?
 
I'll definitely check the driver for the AudioBox.  I can't remember if I installed the ASIO driver.

I think I must have been a little confused.  According to the Presonus specs, the Audiobox USB (not the latest generation) can record at only 44.1 or 48.  I believe I saw where Sonar detected 96, but I'm guessing that was playback, not recording.  So it may not actually help to disable my internal sound card.
 
The immediate problem I'm trying to solve is that I have sound recorded at 96 from a Zoom recorder.  When I copy those WAV files into a Sonar track, Sonar says it is converting the format, and the project shows up as 44.1.  As I am not actually doing any audio recording through the Presonus, I'd like to think that I could create a 24-bit 96 KHz project with the current hardware.
 
When I look at the Presonus
 it doesn't actually say anything about being able to play back at 96, but I could swear I say Sonar go through an analysis and it said 96.
 
So I guess I need to experiment a little more.  It won't kill me to work at 44.1, as these are live recordings of modest quality in the first place.

Thanks CJ.  I think probably about 97% of the recording I do would not make any difference at CD quality.  I have done some in-studio recording of flute quartets, for example.  I think it probably WOULD make a difference in something like that.
 
And I assume that using MIDI composition to some of these great synths could make a difference at 96KHz.  Do you agree with that, or do you think the synths really don't have much nuance that would be picked up by the extra resolution?
 
I am good for now at CD quality.  What I have done so far sounds really good, so I don't feel an immediate need to upgrade.  My first priority is to get a motorized control surface, now that I understand how that will boost my productivity.  But I am trying to get a sense of just what kind of hardware is necessary to have something approaching the capability of a "real professional" studio.

In windows eight, Windows button plus X then the letter B. Click presentation mode before you start mixing of recording. -This only works for computers with a battery.

I'm just noticing that you don't have an interface that supports 96. Sorry about that. My advice is largely worthless.

And presentation mode does exist in Windows seven but I don't know how to enable it.