Furutech spades on copper cables

You shouldn't have any problems with mixing different metals on your termination.
Experiment until you find what you like.

The primary thing is to have a VERY tight connection.
If you cannot crimp the wire into the spade opening tightly, then it will not be nearly as good. Even getting a little smooth face vise to clamp them down would work. (having a oval half circle tube like or whatever form in it to squeeze the crimp properly would be even better.
I have a hydralic crimper. not the worlds best, but what it crips stays crimped!
An alternative is to us some screw and have it just right to capture the wire in the sleeve tightly. Or a solid copper wire you can fit in to fill the opening completely before soldering. Sloppy (loose) crimp and then solder is not a good idea.
If this is hard to do. Then best to buy spades with a built in screw to lock down on the wire.
I use WBT, they are expensive, but will last forever. Even if you change cables, they are easy to reuse.

Elizabeth says,

I have a hydralic crimper. not the worlds best, but what it crips stays crimped!

I second her use of the hydraulic crimper (like the one linked below) that I used on some pretty high quality speaker cables I assembled. Using stranded wire cables, the test crimp I tried almost appeared to be a continuous piece of metal between the spade and wire. Obviously not as good as the new machine Cardas has been using, but as good as I have seen from typical consumer crimping devices.

http://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html