I'd agree with Golurk to Top B. I'v been using both the Stealth Rock setting tank and the Rock Polish Sweeper and they're both very cool. Being able to spinblock one of the most popular spinners (Sandslash, yea it sucks but it's everywhere on the ladder) is a really cool thing to do, and with the proper EV's you can even survive Kabutops' Waterfall and OHKO back with Earthquake from full health. The Rock Polish set is probably one of my favorite users of the move along side Aggron, being able to break down many offensive teams with just a single turn of set up which isn't that hard thanks to it's excelent typing and good natural bulk. Thanks to Iron Fist Shadow Punch isn't a completely useless STAB like it is with Dusknoir, while it also gives Drain Punch a boost giving Golurk a form of semi reliable recovery.
On the subject of Magmorter it reminds me a lot of a poor mans Moltres with it's beautiful offensive STAB, ability to dispatch of Slowking, and it's even better type coverage giving it the ability to decimate many stall teams not fully prepared for it. However it's typing, while being one of the best in terms of offensive STABs, leaves much to be desired defensively giving it a nasty Stealth Rock weakness (not as bad as Moltres though, and it shares good offensive synergy with the best offensive spinner in the tier). With paralysis support it destroys offensive teams but without it often times I felt out paced thanks to falling just short of that base 85 benchmark, and also prone to dying faster than I'd like thanks to it's low defense, lack of recovery, and with with Life Orb recoil potentially taking it's tole. But it's definitely a nuke that's going to do some severe damage if it gets in on anything slower, so with all that in mind I think that Top B is actually pretty solid for it with it's ability to decimate stall and bulky offense but requiring more support or packing less power than some other similar mons above it such as Emboar or Moltres.
On the subject of Magmorter it reminds me a lot of a poor mans Moltres with it's beautiful offensive STAB, ability to dispatch of Slowking, and it's even better type coverage giving it the ability to decimate many stall teams not fully prepared for it. However it's typing, while being one of the best in terms of offensive STABs, leaves much to be desired defensively giving it a nasty Stealth Rock weakness (not as bad as Moltres though, and it shares good offensive synergy with the best offensive spinner in the tier). With paralysis support it destroys offensive teams but without it often times I felt out paced thanks to falling just short of that base 85 benchmark, and also prone to dying faster than I'd like thanks to it's low defense, lack of recovery, and with with Life Orb recoil potentially taking it's tole. But it's definitely a nuke that's going to do some severe damage if it gets in on anything slower, so with all that in mind I think that Top B is actually pretty solid for it with it's ability to decimate stall and bulky offense but requiring more support or packing less power than some other similar mons above it such as Emboar or Moltres.