Selling My Old 20", Early 2008 iMac For 500 USD

Hi,

I have a old "20- inch, early 2008 iMac(but bought in 2009)", and a second hand AirPort Extreme.

I'm planning to sell them and get a new 27-inch iMac.

Someone has offered me "500 USD" for my old iMac and the second hand AirPort Extreme.

Is it a good deal? Should I "sell my iMac, or keep my old iMac until it cannot run any software anymore"?

"

CPU：2.4 GHz Intel Core 2 Duo

Memory：4G 800 MHz DDR2 SDRAM

Graphic：ATI Radeon HD 2400 XT 128 MB

HD：500 GB SATA II

"

Thanks.

Ed