Ive been using OSX now for about 2 months and love it, however im now at a dilema point

The last few weeks the system has been really slow, Ive googled lots of blogs on speeding up the OS, clearing caches etc. freeing up space, Read about what is and isnt defragged automatically, which ive done but its still a bit sluggish. Reason im affected is that the wireless/internet speed is being affected in any browser due to the busy system - my xp pc is fine.

I know what you may be thinking - more ram required, but its been working ok, and yes, i only have 1GB currently on this dual core box, and intend to upgrade, however im really only using minimal apps - firefox...the odd torrent, never two apps open at once.. There is still plenty of 'green in the memory usage monitor.

Being from a WinRott background, i would just reload it but it will be a right pain on this machine as ive got backup schedules, custom kekts, configs etc I did on the fly all configured, things like that. - and ive forgotten my procedure for install too (what kexts i do and dont install after much trial and error) + lots of jigging etc with partitions, etc. I also dont hear many people relaoding their box in years and years so it must be something Im doing.

Could someone give me some advice on where i could look to speed up the box? I downloaded mackeeper which cleared a bit but not a great amount - ive also not found a defrag thats any good on the fly - unsure how i could dismount my System drive (i use a lot of BIG files that i move from disk to disk causing fragmentation beyond the auto)..

Where would you start?