Dell XPS 410 upgrade? New build?

Good day to all experts. I am a novice at best and have done some hardware work and assisted new builds but now have questions and a budget for this project. I need to get more performance out of my only desktop. I have two laptops that are better performers but need this desktop to do browsing, photo editing and business software. I run adobe CS4 master suite, do shipping, printing, video editing and run quickbooks from this pc.

Dell DXP061

Pentium D 2.8ghz

1022 MB Ram

Nvidia GeForce 7300 LE

I have two good optical drives and 2- 250gb HDD's

I know the power supply is low quality and must be replaced.

Don't know how to tell if I have a P965 motherboard or not. How do I tell?

I know I need more more RAM. Thought I had more. Think I made a mistake with the pairs.

If I have the P965 can I go quad core QX6800?

I'm not real comfortable with processor upgrades but have others to assist and hope to have some of you to watch my back.

Video card. I have no clue. Need your help.

Can all of this be done on a decent (less than $500) budget? I am not a gamer. I don't need the best graphics but know I need better than what I have now. Can't even watch my Blu rays on this even though I have the drive.

Am I better off taking my HDD's, optical, keyboard and mouse and putting them in a new tower with a strong power supply and new motherboard and processor? Is that more cost effective? I know that will allow me more upgrades to new technology in the future.

Is there an advantage to buying a kit and using these or maybe just buying a newer used system and upgrade that?

I really need some great professional advice. You folks are my guides and I trust your educated advice.

Thanks for all you do.

via Bleeping Computer Last 20 Posts http://www.bleepingcomputer.com/forums/t/513402/dell-xps-410-upgrade-new-build/