szekeres amp - irf510 equivalent

i'm building the headphone amp at this link:
http://headwize.com/projects/showfile.php?file=szeke1_prj.htm
i tried to get the irf510 or 513, but the seller has none.
he gave me irf540 instead, will they work?
i'm lookink at the datasheets, but i'm quite a newbie so I'm not sure

another question:
there's also a version with a lm317 regulator instead of the source resistance.
what sounds better?

thanks
Nicola
 
looking at the datasheet, the 2SK216 should be perfect, but I can't find it in the catalog
what about the irf 710? it has lower power than 510, max current is 2A
I think it could be a good substitute to the irf510:
irf510 has 135pf capacitance, and at 300mA vgs is between 4V and 5V (but you can't really tell from the graph)
irf710 has 135pf capacitance, at 300mA is around 4.2V

however rds(on) for 710 is about 6 times higher than 510, does that make diference?