the amount of shots blasters can put out on the move or standing still is quite impressive, and the blastmaster while pricey is good against those bigger things so use that one at your own discretion, but also fyi the niose marine box only comes with 1 blastmaster and 1 sonic blaster, so you would probably be better off getting a box of normal csm and going to the GW bits page and ordering their niose marine kit, and as for standard marines, they can act as fairly good tie up units since they are much cheeper than your niose marines, good for getting your marked marines into CC or having them as a counter-attack unit so your niose marines can keep shooting those plentiful shots of the sonic blasters, lesser daemons are also good at this and cheeper but do die faster
So simple, use niose marines with max sonic blasters(since if you dont might as well take marked standard marines) and use those in conjunction with marked standard marines to keep your niose marines shooting, and take the blastmaster, see how you like it, if you do keep it, if you dont toss is out, that one is really for preference
Hope this helps and good luck!