- 64Bit OS (speaks for itself).
- 4-8GB or more RAM (RAM that is not being used is waisted RAM, no harm in using it they are there to be used).
- Very fast internet line (for example 32Bit crashes when reaching a certain RAM usage cause it can't keep up when more RAM is needed).
- Having loads of torrents, big sized torrents, downloading and uploading at very high speeds (RAM is also needed for these things).
These would be my advice to use a 64Bit client instead the 32Bit one.
Stick with the 64bit version from Dayman if it works as you want, fusk

Did you tried running qBittorrent with the OS cache off in the advanced settings? I've being experimenting this and have it off for some time now (with 64Bit qBittorrent v3.2.3) and kinda like it more than when its enabled (by default).