Thanks for getting personal with us, I didn't mean to put you on the spot like that. I figured that was a possibility because once someone says how much they loved a piece of equipment only to get rid of it, it tends to be money-related or they're just weird like me who does it all the time.
First, most three-piece bands sound great when the bass player takes some liberties in adding their own flavor to the songs. Your guitarist must have had an incredibly large ego! No loss there. In time, find another three-piece, but this time tell your guitarist mate that you hope he or she likes a moving bass because you're not sitting on the root all night.
A correction, when I wrote about the 410s, I didn't mean a single cab but the combination of a 210 cab with your 500, thus bringing the count to 4 ten-inch speakers. Personally, and I know it's politically wrong, I like the combination of a 115 with a pair of tens. I think it helps to go with the same brand/line of speakers, as with the Rumble line, but I love the sound of it all. I don't think we're alone in that thinking either.