Ok, long story short:
I bought a 1TB USB HDD to use on my 64-bit laptop (Pentium P6100 2Ghz, 6gb DDR3, USB 2.0), loaded Ubuntu onto it, and installed Armory and Bitcoin core.
It was the same deal as I had on the 32-bit machine: Gave it afew days downloading, then it froze and I had to reset it once ...