Ive had various motor configuration to my 05 Copperhead...stock, bolt ons, tune, paxton, vec3, more bolt ons, built motor, sct...installing & testing many different bolt ons in the evolution process here as well.
One of my favorite setups were stock motor + basic bolt ons + dyno tune..520rwhp
My ultimate favorite, what i have now, built motor + good heads & cam + good dyno/road tune....650rwhp. its nice to have the motor more than comfortably handle this power with complete reliability. With built motor, costs go up and everything must be perfect so therefore a motor pro is a further stones throw away.
I personally didnt like the Paxton, it was making over 700rwhp on dyno and honestly it didnt feel as lively as my built motor now. The Paxton throttle response wasnt that good for some unknown reason however everything on motor was running real good from tuning, dyno, mechanical standpoint.
With the Paxton, I agree with a the others in this thread commenting about the poor feel of the Paxton setup regardless of the high dyno numbers
http://forums.viperclub.org/srt10-srt10-coupe-discussions/642043-supercharger-srt10-08-a.html
From comments made in the above post, part may be due to rear gearing that made Paxton have a less than mediocre "seat of the pants" feel. I had 3.33 rears and car still didnt feel like 720rwhp and i had very aggresive timing map... Paxton car only felt fast when at WOT and for brief rpms going from 4500-6000 WOT. Part throttle sucked for a 700rwhp car, and like i said above everything mechanically & electronically was running good and if it wasnt, it sure couldnt be found. everything with tuning, codes, A/F wideband & boost gauge sure looked good. Maybe it was the BBK TB holding it back, but paxton throttle response just felt lackluster... That BBK TB was the worst Viper mod ever!
With a S/C we have more hp, but we really only have more hp under boost, so lower rpms & part throttle dont count. Add this to the viper slower winding motor...so a little of all of that hp delays add up. I dont drive at WOT often, but thats just me.
Paxton performance also deterioted quickly as motor heat soak developed and it sure was noticeable on mildly hot days. A car with that must hp should be insane fast in any rpms...anywhere & anytime...no excuses.
With the paaxton you just really need to lay into the throttle allot to feel the power which is contrary to what my idea of 700rwhp should be.
With the Paxton, The front end was also 100lbs heavier ahead the front wheels and handling suffered some.
Becoming more of a purist I also no longer believe there is any reason to have Forced Induction on an 505 cube motor unless your interested in 1000+hp
Shops are doing 620+ on good heads and cam and bolt ons with stock motor... thats good power, but everythings relative so ultimaltely depends on what the owners performance goals really are. Thats a tough question in itself sometimes.
I would personally pick the good heads & cam and tune make everything as perfect as can be using the best vipers shops around and be satisfied with that. Sure the heads & cam may prove more dollar per hp than the paxton however we should consider what really makes a good motor too.
I believe in the range of 650 hp at the crank. 
