Time for a hand held 3/8 impact driver with a high quality mm bit. It will help seat the bit in the allen head and the force from the hammer blow will help to loosen the grip the threads have. These do not have to be that tight, I use a cycle t-handle allen wrench to loosen and tighten mine. If you strip the allen heads out, you'll have to drill the heads off, or try one of those broken bolt removers that fit a reversing eletric drill. If you drill the heads off you can remove the filter retainer and then turn the bolts out with a small vice grip. Max

If you dont want to go for the tool first, you can try this. With a small 1/4 drive deep socket & extension over the long end of the allen wrench, put some pressure on the thing, trying to loosen it, but dont try real hard, just enough to flew the allen wrench a bit. Then, lightly start tapping on the socket, open your fingers & hold down on the extension & it should flex & slap your hand with each tap of the hammer. If you have a light hammer, like a body hammer, that would be great. Or, a 10 inch long 1/2 extension should do it. The idea is to increase the pressure just a bit, feeling of it, since you already know what stripping one feels lie, you know when to quit. Working the heads to close them up is a great idea. Doing it before the wrench slips all the way is a better one. PLacing something, seems someone suggested a socket? on the head of the bolt in the oil filter cover & smacking it to shock the thread is a grand idea. Surely you wont have to buy an impact driver, but if ya do, they arent expensive.

I went to Sears and bought a set of cushioned 'T' handle metric  hex wrenches.

That way, all the torque from twisting is centered on the head of the screw instead of on the shaft of the wrench..

$20.00 for the set and you'll ask what took yourself so long to get them...

Some people are definately over tightening these things. It's only a rubber o-ring. It doesn't need 85 ft.lbs. of torque. You don't want it too loose, but geeze, they don't need to be that tight. Not sure what the proper torque spec is for those. I work on cars for a living, so I kinda got a feel for how tight is tight enough.
When you're re-installing them, send Johnny Beefcake home and let the gasket do the sealing. (Same goes for the drainplug--should never need a hammer to loosen it.)

Yep, small bolts, aluminum threads in the case, rubber gasket on them...just a nice snug turn of the wrist is all that is needed.  
I rarely use a torque wrench on little bolts like these...it is all in the FEEL of the "turn of the wrist".  If you go easy and take your time, not doing a hard-n-fast turn to crank it down, you will feel the steel threads of the bolts  taking hold of the aluminum threads of the case, feel the snug contact and feel the alum. beginning to stretch as it gets tighter.  That is when it is time to stop.  I would bet that the torque at that point is within 5-10% of the book torque value.
For some reason I can just feel it ... don't know why, I just can.

Too tight bolts - Oh hello preaching to the choir!

I ended up pushing the wrench with my FOOT to get the oil bolt off, and had to whack the side cover screws with a hammer before they came loose.
Also, something not mentioned yet - spray them with a lube like WD40.

Keep at it - if I can do it YOU sure can!!

And if it's nuts that are too tight.... well.....