A few days ago I went to BestBuy and spent $20 on a cassette aux cord (I have a Mach 460 system as well) Insignia 3' 3.5mm Cassette Adapter NS-CA103 - Best Buy
Other than that, you'd have to buy an aftermarket head unit that had an aux input
I have an 04 with the mach460 and added an auxillary input to the satellite radio port. When I push the 'sat" button it reads "aux" and runs to a 3.5mm jack that I can plug into any ipod, iphone, etc. I cannot for the life of me remember the part number or where I got it other than I did a google search for the part and found the website. I know that your radio has to have satellite capability in order for this to work.