If 450HP is not enuf, and you are "equipped" to handle a 550+ HP monstor, sometimes less streetable than stock, "Tuner Cars" can be had for a fraction of the cost of the mods.
A wise man here told me that a rule of thumb is "used Vipers yield normal prices, plus 10%-15% of the value of the mods."
ie....a $20K in mods might only add $2-3K to used retail price! A cheap way to get a lot of mods, IF-IF-IF the car was cared for and you can bear the risks associated..........
If 450-480HP lites your fire, and if you value a warranty, and have 60K to spend, buy the newest, lowest-mile used OEM Viper you can find, with only must-have bolt-ons like cat-back, tubes/filters, and some common cosmetic {MGW)upgrades.