While 50K is a solid chunk of money, if you want truely fast you really don't get reliable with it..
You can probably find a stage 2 or stage 3 Roush Mustang, which is what i would classify as Fast, or boarderline Very fast.. But they aren't rock stars on reliability..
Where a Lexus will be very reliable, but not really fast.. "quick yes" but not what i would call fast..
Typically i would suggest spending 20K on a cheap reliable daily driver, and purchase a used 09+ roush stage 3 or 429R mustang, they are still 500+ HP and can be found for 25K or less with less than 20K miles on them.. which is cheap, and fast.. and for the purpose of a toy, reliable..
The only thing i can think of that might be fast to some people is the WRX STI which is reliable, relatively cheap, and pretty quick...