So, I am loving the game but the sound is lacking bass big time. The sound coming from the backbox speakers sounds good, but I barely hear the sub. I don't want to use an external sub because I have issues with floor space....meaning I don't want anything under my games. Has anyone tried Pinball Pro's original MM kit

http://pinballpro.net/shop/medieval-madness-complete-kit/

or Flipper Fidelity's kit

http://flipperfidelity.com/sound/williams-bally-speaker-systems/williams-bally-complete-replacement-speaker-system-for-wpc95-machines-430.html

I'm not sure these kits will sound/work better with MMR with the newly designed uncompressed stereo hardware.

Thoughts?

OK, thanks Yancy I'm going to wire-up two new coaxial 5 1/4" the way you did.

Are there any options for more bass without using an external sub? I'm thinking a shallow mount sub to clear the troll mechs.

Possibly something like this?

http://www.crutchfield.com/p_130TSS2002/Pioneer-TS-SW2002D2.html

It's got dual 2ohm voice coils, so if I wire it in series I should get 4ohms like the stock crappy sub, right?

Well, I wanted to do some testing, so I pulled my Rockford Fosgate Shallow Mount 8" Dual 2ohm Voice Coil Sub from my 4runner and wired it in series. The result was better, but still no where near the bass of my Walking Dead with the Flipper Fidelity kit.
Granted the Rockford Fosgate is not a free air sub, and the Pioneer I was looking at is, so that might might make it a little better.
I was happy it cleared the troll mechs though even on top of the stock spacer on the cabinet.