i've never played a marshall acoustic amp. every amp has it's own characteristics. acoustic amps, generally, are trying to emulate the sound of the acoustic guitar. most of them are digital, so, they are trying for 'accurate reproduction', which is the same thing a pa is supposed to do. i have no clue what putting a multieffect unit in between guitar and acoustic amp would do. generally, most 'electric guitar amps' have some distortion, which is-strangely enough-what most of us who play electric want. fenders are known-again, generally-for 'clean', but they also will do dirty, as will many other amplifiers. i have a couple of 5 watt electric guitar amps-at quarter volume, their 'clean' will sound different with different guitars and pickups.
it would be a good learning experience to go to a music store and play through some different amps with your viking. it might save a lot of frustration and money for you.
