A brand new receiver alone will already cost 15k at the least.
If I had 20k I would shop around at the Buy & sell section of PDVD. Terrific bargains there.
Get one of those pre owned receivers from 7-10k & get a pre-owned 5.1 speaker system w/ whats left.
If you can, save up for more (maybe at least 40-60k). Instead of settling for your budget now & ending up w/ endless upgrading, you will waste
sooo much more time & money in this path.
I know this so well, cuz I went through it myself
.