As for the question at hand. If you go with the pdi hop up chamber, I recommend a good aeg bucking and barrel. For the bucking, guarder, systema, prometheus, G & G, etc. work fine. As for the barrel, I love my prometheus 6.03mm barrel. Works well with madbull bbs, and is pretty solid (will not bend easily). I believe the mbo5, being similar to the mk96 or other l96 variants out there, that the barrel length is 509mm. I actually cut mine down to 499mm so that I could keep the end cap on. If you decided to go with a flash hider than there would be no need to cut anything.
Also, if you do get the PDI hop up chamber, get a few of the repair kits with it. The o-ring breaks easily (maybe thats because I dissemble my rifle too much
). Also, if you were to lose any other bits and pieces, than you have a few at the ready.
And whichever bucking you end up using, depending on your rifles FPS, I would recommend a particular nubbin. I use the prommy nubbin in my rifle shooting around 450 fps I would say. Works well, given the nubbin is a soft one. When I used the hard nubbin (one that comes with the PDI hop up chamber) it would give the bbs too much hop, even with the screws tightened all the way in (less hop). So depending on your fps output, thats something to think about as well.