There are some really good deals on vipers to be found. I bought my 99 ACR in October and got a REALLY good deal, all stock with 3400 miles (boughtin Mountain View). the 97 rt-10 for sale in the classifieds NOW for 43K with 23K miles on it is a probably a really good deal considering its scarcity ( Gen II, Gen I hood, < 100 built that year).
Modifications should not be considered a bad thing, in particular, exhaust systems. The stock exhaust really sounds weak, and is the first thing most owners modify. I have still not done mine as i'm not sure whether i what to go with headers or not, but it will happen sometime soon.
Vipers before 95 or 96 had head gasket problems you should be aware of not to mention no windows. As Gerald mentioned you can put side pipes on any car. If you are interested in a driving experience consider coming down to Santa Cruz and we can go for a spin. Also, check out the viper club meeting in Campbell (near Los Gatos), it's generally worth it. about 20 cars show up from my experience. There is info on this site about meetings. They are the 1st tuesday of the month.
see
http://www.thomasser.org/viper for differences from year to year and some other info.
Jason