I know your PC is a Laptop you can tell just by the stats
Build a machine yourself is the best option
But even buying a pre built machine is fine as well as long as it can have graphics/sound, cpu & memory upgradable getting a new motherboard is also an option if you take it as far as it goes but still want more as you can still use graphics cards sound cards memory ect in a new motherboard
the 3 main things are Memory Graphics and CPU
Intel is the cheap mans graphics and is not the best to be honest, N-vidia or ATI Radeon are the bester ones but you don't need to jump to those off the bat
You can start off small and make your way up, though I would still go for CPU to start with as those can epic fail when you install them
I wouldn't know what is the best budget machine for both price and performance I also could do with a desktop machine
If you are wondering though I have a 2TB drive hooked up to my Wii, currently not setup to run GC from the drive though my Wii is old enough to run direct from disc, anyway the HDD has 3 Partitions on it 2 WBFS formatted partitions for 1000 Wii games and a FAT partition used for emulators on the Wii with full SNES NES Mastersystem & Megadrive rom sets.
At some point I will re-format the 1st WBFS partition to FAT for GC games (or split it into 2 again so I have 4 partitions), just not got round to it, too busy playing on my PS3 360 and 3DS, I do tend to go back to older consoles as well though