Cable: $20
Strap: $20
Strings: $25
Case: $20
Rumble 500 combo: $600 (Because they are awesome sounding, have some nice built-in options, and are loud as heck.)
Ibanez SR655: $750 (Love the sound of the Nordstrand design pickups)
With the rest, I would buy a stand and some items to do a quick setup. Possibly also a pedal tuner.
If the accessories did not count in the original sale and if sales tax was excluded, I would upgrade the bass to a BTB675.
The above was in the spirit of the original post. The following is what I would really do.
I would go to the local Music Go Round, buy the best bass and amp I could for about $1000 and get them to throw in the strap, cable and bag and I would buy some strings there too. Then, as my local MGR allows, I would borrow some tools, do a setup onsite and get to my gig with plenty of time, way better gear and about $475 in my pocket. If they had a USA Peavey bass, I would escape for a whole lot less.