i love to use video-mixer setups.... (got an edirol v4 and some other old fashioned mixers) see my signature for possible setups... now i mostly use my new schenker notebook... for one beamer with mapping or a simple panorama (with matrox) the 650m is fast enough... if there's more to output i use m...
did you tried the Trails effect? :p
i think you should be happy with it... also can freeze the screen completely (without trail) if you set the trail from 0 to 100 (with midi/keyboard/osc mapping for example)
i once played in a planetarium... we used a big glass prisma and one powerfull beamer for the whole dome.... resolution clearly wasn't the best but anyways it looked awesome!
normally there are i think about 32 Dia-Projectors which are stitched together to get the dome projected....