Well, I thought I'd post some thoughts on these two amps, since they will likely be on the list of possibilities for some people. I've been playing with the iamp 800 for about a year now, and just got my ag500 up and running. Understand now, I'm really only looking for one sound, something I can hear on stage in loud loud bands and will have some oomph in the tone section. So versatility is not something I'm looking for. I've always found the Iamp to be a little dissappointing, which is why I bought an ag500 in hopes of the vaunted aguilar plug-and-play tone. I'll post comments based on the situations I play in: Rehersal: I stacked both amps so I could A/B them through the my aggie 112 stack. I was actually pretty surprised at the similarity in sound between the two amps. The iamp seemed like it had a little more in the low end. The aguilar definitely has a "sound" to my ears, while I can see that people who prefer something with less color would choose the iamp. I liked the coloration. My basses still sounded like my basses, but with a little more oomph and a little more evenness across the neck. I could hear the notes on the d and g string a lot better, fuller tone for higher notes. This was a fairly quiet band, so either amp was fine for volume. This band also leaves a lot of room in the mix. This round went to the ag500 for me. Gig 1: So I was expecting to be blown away for this gig given how the amp sounded during rehersal. Too bad, so sad. I brought just the ag500 (no switching during gig) to play with my schroeder 410. I would say it was probably louder than the iamp, but the tone which had cut through in rehersal still got eaten by the guitarist and drummer. This is a different band, they are unbelievably loud and don't leave a lot of room in the mix. The notes on the d and g string were a little clearer than in the past, but I was a little underwhelmed. Mind you, I didn't have the opportunity to fiddle with the eq at all. Not the kind of review which describes the tone of each amp in poetry, but I'll post more after I bring both amps to 2 rehersals this week. If people have specific questions about the 2 heads, I'll try to answer . . .