I would do the stereo and maybe the K&N. The stereo you can take with you to a new van and the K&N will save $$ on filters. Its a 10 year old van, probably worth 1500-2500. I wouldn't drop too much into it.
exactly what i was thinking... a good stereo system is a must for something you spend that much time in. and a k&N filter is a worthwhile buy for any vehicle.