GS Wavetable Synth MIDI to Audio

Okay, after reading around on the forum, I've gotten the impression that the Microsoft GS Wavetable Synth is not recommended.  While I wholeheartedly agree (to a point), the initial track in a first project I have been working on was made with this.  I used other Cakewalk softsynths for the remainder of the project, yet this track remains and I happen to like it as it is with the GS Wavetable Synth.  I toyed with other softsynths to try and produce a comparable sounding tremolo string but could not produce quite the same sound that fits like GS one does among the other tracks.
The manual and Sonar 8 Power! each have fine instructions for converting the MIDI into Audio and that works great for everything else but for some reason I cannot seem to convert the GS Wavetable Synth track.  I've read on this forum that converting GS Wavetable Synths to audio is basically impossible.  I'm wondering if that is technically true or if there is just a bias against it.  Even though it is GM, I'd prefer to be able to use every tool in the toolbox, GM or not.
It seems to me that it would need to be recorded in an audio track from the MIDI data as per the instructions in Sonar 8 Power!, but I may be wrong.  Since it is an external softsynth (at least as far as Sonar would be concerned), one would think that it could be selected as an input for the audio track so that the audio produced by the M-Audio interface I'm using could then be rendered to the audio track as an actual waveform.  However, GS Wavetable is only available as an output and I don't see it listed in the MIDI Devices menu as an available input in the first place.
Is there a way to do this and still preserve the track with GS Wavetable or will I be forced to sample the playback externally and re-import it as audio?
Any help would be appreciated.
Thanks in advance.

You gave me an idea that worked great.  I was trying to get it to record internally but kept getting errors or just plain having trouble with playback and recording at the same time even though my interface (M-Audio FW Solo) should be able to do that.
So I went with the external cabling idea, straight out the stereo headphone jack to the double inputs in the back.  It actually worked rather well and any difference in the sound quality seems imperceptible.  I knew that little 3' stereo-to-double-mono monster cable would come in handy at some point!
The TTS-1 works nice for some of the other synth parts and that exports fine, it's just that the tremolo strings don't quite have the same feel as the GS Wavetable - like you said the sound produced depends on the synth.  If I took enough time, I could probably manipulate one of the softsynths into producing something very similar, but it still wouldn't be the same thing. 
When I said externally in my original email, I wasn't thinking about outside the computer.  Thanks for the nudge in that direction.  Eventually I'd like to get to the point where I can trigger external synths and such but I'm not there yet.  Another small step forward I suppose.  Thanks again.