Replacing plug cables...

My '01 XJ has about 60,000 miles, thought it might be time to change out the plug cables. I'm using Bosch 4-point Platinum plugs and like them, but wanted something of an upgrade with the cables. The stock cables are housed in a sort of long bax that runs the legnth of the engine. Anyone know if this is an easy replace or must it be stock?

Thanks.

that long box is the cables/coils, it is one single unit and it cost $127 from the dealer. Dealer claims they rarely go bad, if at all.

So an after market replacement is out of the question? I'd love to get better performance.

I have never seen an aftermarket performance replacement in all my searches either. The only thing you can do is replace the boots if they go bad/get worn. ($20-$30).
HTH
Nathan