I skimmed [2] and it seems very interesting.

Still, regardless of whether P!=NP, it is known that P is contained in NP which is contained in PSPACE. These classes are defined for certain computational models. If you change the computational model then those definitions might not make sense.

>Some non conventional computers [1][2] do exponential space in polynomial time.

For under $500 ...

As a re-representation of the DNA computing work cited above, you can actually do exponential work in poly time using a photocopier.

EDIT: here's a link to a paper describing this approach: http://www.springerlink.com/content/j5213p8761224304/