Yes adding more RAM would increase performance considerably
I thoroughly recommend Linux Mint 9 Main Edition which is built upon Ubuntu 10.04 Its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled
Linux Mint 9 Download
http://www.linuxmint.com/edition.php?id=52
The Perfect Desktop - Linux Mint 9 (Isadora)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-9-isadora
Linux Mint 9 User Guide Download pdf.
http://www.linuxmint.com/rel_isadora.php
You download the ISO. image of Linux Mint 9 then you need to create a Bootable LiveCD for installation
Linux Mint 9 can also be run direct from the LiveCD from Booting up without touching your Hard Drive
Also worth considering :
Fedora Remix (Fedora with elements of Linux Mint)
http://www.linuxmint.com/blog/?p=1418
http://fcoremix.wordpress.com/2010/05/25/lucky-13/
http://iso.linux.hr/community-fedora-remix/
Again Fedora Remix can be run direct from the LiveDVD without touching your Hard Drive
Take a look at DISTROWATCH.COM where the possibilities are endless. Create as many LiveCD's of different distros. as you want to find one that suits you
http://distrowatch.com/
Major Releases
http://distrowatch.com/dwres.php?resource=major
LUg.