Hardware Question about Authoring

[Megadeus Ver. 3]

My current system is:
ECS K7S5A Rev. 3.1
AthlonXP 1800+ (No O.C.)
384mb SDRAM (PC-133) ****
2 40gb Western Digital HD (5400 and 7200) ****
Win2K SP3
NTFS

The other stuff I believe is un-important to the question, which is:

The 2 items listed above with **** I am considering upgrading to the following:
512 DDR PC2700
One HD 80gb 7200rpm 8mb cache

With the above upgrades, what type of performance increase would I see?
Currently I can convert an avi to mpg2 using Vegas 4 in about 20 hours.
I prefer Vegas due to the quality of the mpg2 file. I've tried TMPGEnc+ but I just don't like the quality of the output.

Any and ALL replies are always appreciated!
Thanks

[yf2001usa]

A new harddisc give you more space and you need 3 sets of files for authoring. the source, the converted stuff in mpeg2 (about 4,7 GB) and the final product (about 4,7 GB)

More memory will speed up your encoding time a bit cause tmpgenc will be able to read more out of the memory of your computer which is faster then your harddisc. But for authoring the time reduce will be less cause i can author a dvd with (AMD 1,8 with 512) in with in a hour.