Well, in order to produce 64bit binaries you would need a 64bit system (although maybe with QEMU you can omit that but it's not worth it). RAM-wise it's no problem to stay with 32bit because of the PAE (physical address extension) that is a feature of the Linux kernel that you either already have with your current one or need to add (by downloading a PAE-enabled kernel image). For more information on PAE you can read at https://en.wikipedia.org/wiki/Physical_Address_Extension. Your CPU has to support this extension (from what I've seen at http://www.cpu-world.com/CPUs/Core_2/Intel-Core%202%20Duo%20Mobile%20T7700%20LE80537GG0564M.html in the section Other features at the bottom it does support it). You can also check http://unix.stackexchange.com/a/12071 on a discussion whether to use 32bit with PAE enabled or pure 64bit OS.