Upgrade Digi 003 rack?

[KerryCalvert]

I am using Pro Tools 2020 with Native Instruments plugins, mostly Guitar Rig 6.

I am very disillusioned with the quality of the guitar effects this produces. There is no effect that produces decent sustain in the high notes, and most of the effects are heavy distortion and modulations that are boring. Trying to reproduce tones of the major guitarists like Gilmour, Satriani, Van Halen, Carleton, etc seems like a impossibility with this rig.

My 003 is 20 years old now, and rarely used because I have never been happy with what it can do, going back to PT 8.

Since PT 2020 does not officially support the Digi 003, I am considering upgrading my audio interface to a more modern one. Along with the tone weakness, this setup has a lot of problem with hum generated from poor cable ground, in spite of my efforts to follow the normal corrections for this problem.

My question is whether upgrading the audio interface will help me solve the tone quality issues or hum problems. And if it will, what setup (hardware/software) are guitarists using to get a professional sounding rig emulation?

I realize there are many factors, including the guitar, cable quality, power quality, etc. But I have a quality guitar, professionally set up, a Furman regulating power supply that all the equipment gets power from, and quality cables. The constant through all this investment has been Pro Tools, and the 003 rack.

I am obviously missing something.

My assumption is that the tone quality is not a primarily a function of the input signal from the 003, and is more an issue of the plugin software or CPU speed to do the signal processing. But maybe this is wrong, and there is actually signal conditioning happening in the 003 that is poor?

I am using Windows 10, on a 4 core 3.4 Ghz pentium and 16 GB memory.
I have the Digi 003, and a Tascam 8/8 pre-amp. I have tested connecting the guitar directly to the 003 as well as the pre-amp, and there is no difference in the tone quality or cable grounding issues.

My issues are not related to recording, I cannot get a decent sounding guitar platform just from setting up the mix and playing to test the sound.