Picking a Pipe?

Hello everyone. I'm trying to select a nice performance pipe for a new build. It will be a china girl 2 stroke, 69cc, balanced crank and ported. It's going to be direct drive with the possibility for a shift kit later. I'm interested in recommendations. I've been considering these pipes but perhaps you recommend something else?

KTM65--> http://www.ebay.com/itm/FMF-Exhaust...ash=item3f488ff36e:g:EdEAAOSwGYVXBpLh&vxp=mtr

XK65---> http://www.ebay.com/itm/Pro-Circuit...ash=item5428411a0f:g:akEAAOSwUdlWdb0K&vxp=mtr

RM80---> http://www.ebay.com/itm/FMF-Fatty-E...ash=item2c8478b694:g:xbwAAOSwp5JWT-01&vxp=mtr

CR80---> http://www.ebay.com/itm/FMF-FATTY-G...ash=item58dca248b9:g:lGQAAOSwOVpXUiTf&vxp=mtr

KX80---> http://www.ebay.com/itm/KAWASAKI-KX...m45e1890673:m:mmDDMIcytZ2dxMGx5t3PF4Q&vxp=mtr

Are there any major differences between these pipes? What kind of performance can I expect? Which would you choose and why? It's going on a GT2-A frame, will there be any difficulty attaching it to the the bike or the exhaust manifold? I plan on getting a silencer also.
All replies appreciated
Thank you

Okay, thanks for responding, nobody else seemed to have anything to say. I was kinda leading toward the RM80 but still undecided.

Bobby---okay, love to see it

Greg--I understand about getting a proper fit, however, it's going on a new GT-2 frame with a pedestal mount so I should have plenty of room.