Cheapest surround (2.1, 2.2, 5.1, 7.1) headPHONES (not headSET)?

Please leave a link... please.

Surround is a software feature, not a hardware one and whatever hardware implementations do exist are fairly horrid.

Get a regular 2.0 pair of headphones and use virtual filters to achieve 5.1 or 7.1.

Either way, i can reccommend you the takstar 2050 with brainwavz pads, pretty much most single balanced armature driver earphones(or rather ones that dont break), the Superlux 681 evo, panasonic hpt600, the brainwavz hm5/any clones of them and there's others and you should probably check head-fi for more recommendations.

Surround in headphones (5.1, 7.1 and stuff) is a gimmick. You only need two speakers to achieve full surround with headphones. All those surround headphones sound like shit.