Congrats on the new car!
You're going to spend $1K on solid rear diff bushing and only $1K on a new suspension?
That diff bushing better be made of silver and sitting on a shelf inside your house.
SPL solid rear diff bushing costs like $150. Even SPL solid subframe bushings are only $200. Coilovers will cost more than $1K for anything decent quality. Not to mention a lot of other supporting suspension bits (full SPL catalog will run you at least $5K in suspension parts).