I'd suggest you take a look/pictures of the BB any numbers or identifying marks should narrow it down. From what I read the majority of square taper BB's are 68mm wide the oversize variant is 70mm width. It's the euro part that's less specific - I do see some indications that euro = english/british thread, if this is true you are golden for the stuff I've posted - and you can get a "real" crank in there. The S100 is as cheap as I would consider at $66 for the Crank and BB, that's going to be hard to beat for something that gets you off the square taper wobble wagon. The S300 is a road bike crank with one chainring, a very nicely engineered crank with the GXP outboard bearing cups and the very stout hollow spindle for maximum stiffness. The only way to get tougher would be a downhill or BMX crank, these will be HEAVY though. You won't flex a s300 spindle and they don't loosen up on there own - although they are easy to work on with just one self extracting bolt.

You never said what's wrong with your cranks or BB, why the need to put something else in there?