I recently did the research on these two models, and while I liked them both, I decided against them and ordered a Furman Powerstrip model (PST-8 Digital) instead. After too many hours of thinking and researching, I decided the Furman powerstrip, at $159, was better than anything else out there at the "below $400" price point.
As far as the 2600 and 5100 goes, I found them to be relatively equal in features and performance. One thing you may want to check out is whether the 2600 will shut off in case of a power sag (say, 95 volts or less). I know the 5100 will (and Panamax is proud of this) and I do not believe the 2600 will, but I'd still call Monster to make sure. Also, my impression, after speaking with industry people, is that Panamax handles surges better and that Monster filters better.
Of course, the Furman powerstrip shuts off at voltage sags, and has excellent filtering technology. The surge protection is top-notch, because it is "non-sacrificial", meaning that it will not "sacrifice" itself to save other equipment in the event of a strike. Furman simply handles the strike, and continues on as if nothing happened. That way, you don't have to buy another unit. If you can't already tell, I am very excited about the Furman Elite line and the Powerstrip series.
Good luck with your search........
