There's not much you can do to it. Just be sure you equip it with a nice set of luxury wheels and a good sound system. I don't think it's a good idea to mess around with the engine or the suspension. If you do something to it let me know.
I have a 960 Wagon and my friend and I have ghetto rigged an intake for it... it turned out to be fairly easy. Buy a normal K&N Filter or generic brand cone filter that would go onto an intake. You need the 3 inch one. If you remove the air box you can fit the filter right in where it should go. This increased the sound and added a touch of power by increasing the effeciency. If you need help email me. We call this the Swede Speed Fix. It's all we have found to do to my Volvo.