Thanks for the advice guys, much appreciated. I ended up running the POD XT pro in the effects loop of my Mesa V-Twin pre amp. The amp mods, especially the distortions, sound fantastic through headphones or direct record, but as part of my live signal mixed with my pre-amp, or even dircet into my 20/20 amp and then into a cabinet, they just are not the same.
I played around with it, with no amp or cabinet mods on, as part of my effects loop, wet/dry around 50/50, until I could hear no apparent impact on my clean tone when I switched it on - because there is indeed a huge difference between the POD XT pro clean tones going direct into the 20/20 power amp and then into my cab vs. just my Mesa pre amp - the Mesa sounds just way better, much warmer, no bitter high ends, you get the point. So when set up where I have either my clean or chrunchy tone from my V-twin pre amp, which the chrunchy is quite nice so no need for any of the modded distortion effects, I can then add in delays, phaser, reverb or any of the other numerous effects the POD XT Pro has to offer, in combination of I think like 4 effects plus reverb - that sound pretty good to me. I have some scratch tracks of sugaree and brown eyed women on my myspace with this set up, the deal track is same set up without POD XT-Pro signal in effects loop. I give it major thumbs up, if you take the time to get the settings right for your rig and guitar. Mostly reverb, delays, and mod effects like phaser or chorus.
As for the Mesa 20/20 power amp, I actually started playing lately it where the volume should be, around 10-11 o'clock on the dials, and I absolutely love it. It gets pretty loud, and unless you are playing a really big club, I think would be sufficient and no need for the 50/50. The amp sounds good at 8 o'clock setting where you won't shake the room, but really sounds good when you can push it and plenty loud to cut through the mix - takes up a single rack space. I also give thumbs up big time.