Router slow Downs?

Hi All,
got a few questions
Been a couple months since I re-built my hp franken machine but now I have a router question. I have a older
D-Link model No #DI-604
on bottom it says
H/W:A2 and F/W1.1
I cant find any ?" firmware up dates" if that would solve my problem,
Which is when I use this router my d-loads and up-loads get cut almost in 1/2 even in something as simple as a chat window I see lag,

I have it plugged into a modem I got from comcast that has a cat 5 output and a usb out and also handles my VOIP(and talking on the phone dose'nt seem to have an effect (eather way) ARRIS MODEL #TM402p/na-1.
I know its not my pc's as when I plug them right into modem their ups and down"s" "scream"
OR is there a router i can buy that will not slow down my pc's.
(wouldn't mind if it was a wifi router w/ 4 port)

Thank You in advance all!! 8)

Hopefully the link that grumpy sent ya works, if not read on: a lot of routers are prone to slow down after awhile, ya have to un-plug and or reset it, then it should speed up. If the router is getting hot(not warm but hot) to the touch, a heat issue will slow it down, I have a D-link DI-524 with heat issues and had to cut a hole in the top and hard wire a case fan on top to keep it cool, and had no issues after the fan install. This helped in my case, but I dont know if it will work for you?

Well you get what you pay for, You will need a buisness class router, but they are very expensive, that be ok if money is not an issue, all router brands has their ups and downs, linksys is over rated. (owned 3 linksys and returned all 3. DOA) have friends who swear by those, then turn around and cuss at 'em. But their is an suggestion, try monowall, it runs on a very old computer(P-100), it is wi-fi with certain wireless cards, runs multible nics, harden firewall/router, and works very well. and does not slow down your connection. Once its set up you dont need the keyboard/mouse or monitor. http://m0n0.ch/wall/ check out their web site!