If it is the Inspiron mid tower there are worse pre-builts to start from.
What CPU is in there now?
There is always the possibility of an i7-3770, but I kind of agree, there is enough of a difference to make that a losing proposition. Though if you could find a used one for a low price it might hold you over while you save up for a new build.
If you were to buy a new heatsink, powersupply, and GPU, these are all things you could re-use in a replacement build.