I have listened to the Audica MPS1 and they have great sound for their size.
An amp and speakers take up a lot more space and
TBH you need to have a decent source to make the most of the amp and speakers you have. Unless you are running an external DAC(or have a suitably decent quality high end soundcard) off your computer you are wasting the potential of any half decent amp and speakers
IMHO. Also another factor is listening distance(and height too) too and the proper positioning of speakers. If you toe the speakers in you need to be a couple of meters in front of the speakers to get the optimal soundstage for the speakers and if you have your computer in a small office or room it is not really that practical to be having a couple of large standmounts or floorstanders cluttering the room and not being properly positioned
IMHO. With loudspeakers I tend to be weary of buying them secondhand unless I could examine them beforehand. You really cannot tell if someone has overdriven a pair and caused damage to the crossovers or the drive units.
For computer listening I tend to prefer headphones. I use a pair of Grado headphones through a dedicated headphone amp and hopefully I can get a TC7510 or DacMagic DAC at some point too.