Help me buy a new PC

I am planning to buy a new pc but i have test driven several new pc's which were recently bought at work and they all seem to be running at the same speed as my computer at home. The computers i test driven are:

HP Compaq dx2250
AMD Athlon 64x2 dual core processor 2.59 Ghz
1.87 Gb RAM
Windows XP Professional operating system

Intel(R) Core(TM) 2 Duo CPU E4500 @ 2.20 Ghz
2037 Mb RAM
Windows Vista operating system

Dell Dimension
AMD Athlon 64 X2 Dual core processor 4200+ 2.20 Ghz
1022 MB RAM
Windows Vista operating

My current PC at home is AMD Athlon 1 Ghz with
384 MB RAM
running windows XP professional
with 8MB AGP graphics

The 3 new pc's all feel to be no more faster than my pc at home.

I need the new pc for every day work such as internet email, web development, some graphic design, movies, DVD's a little gaming, MS-Office, movie editing etc.

I have done quite a bit of research on the web but i cant come to a decision.

I know new pcs have dual core CPU's, are 64 bit, with SATA, good for mutlitasking.

Should i buy a new PC or just upgrade my current system with a large hard drive, more memory, with power graphics card? My current system can take 786 MB RAM, is IDE not SATA bus speed about 66-100 Mhz but the new pcs feel the same.

On each of the new PC's i have run all the applications i need at once, they were all opened at the same time and i worked on the other while another was open. The massive amount of RAM and made no difference.

only the

HP Compaq dx2250
AMD Athlon 64x2 dual core processor 2.59 Ghz
1.87 Gb RAM
Windows XP Professional operating system

made a little difference, it was just a bit more faster nothing jump up with joy about.

i'd go w\ a dell optiplex or vostro. they have some good deals if you goto dells site, they tend to advertise these deals on yahoo, ebay , and other sites. You can usually get a great system w\ 19-22'' lcd for around $500.