If you're running on 32 bit architectures for your main servers you are just playing around and you don't need stuff like varnish.
If you're going to try to push multiple Gbps out of a single box the least you could do is put a bunch of ram in it and install a 64 bit OS. That's a lot more bang for the buck than installing multiple 32 bit boxes with only a bit of memory in each.
Certainly, the "professional" thing to do is install a 64-bit box with lots of memory. But don't underestimate "playing around", especially as it pertains to the popularity of OSS.
If you're going to try to push multiple Gbps out of a single box the least you could do is put a bunch of ram in it and install a 64 bit OS. That's a lot more bang for the buck than installing multiple 32 bit boxes with only a bit of memory in each.