Video card:
the Quadro FX 5800 was released around 2009, it's a very old card.... old generation...
Quadro K4000 old generation too...
It would be a shame to have a new pc, with an old (or even very old) graphics card.
in CG, I would recommend P4000 (which is the current generation)
RAM:
16 GB ECC (32 GB ECC if it's to do a lot of simulation calculations, or photo rendering)
DDur:
SSD (standard "from my point of view" for at least 8 years)
500 GB (although today 1 GB SSDs have become accessible)
Is there a backup system on the network? If the answer is no, accompany with an external (or internal) hard drive (SATA or SAS) to make the backups.
Processor:
Unless it's for a PC-server, or to do 'calculation-render-to-death': it is not necessary to have a bi-CPU.
(we used to use bi-CPU motherboards, to overcome the problem of having little core in the proc, it was 10-15 years ago, today with the proc 6 core or more, it no longer has any reason to be, for a work PC)
a Xeon 6 core (12 threads) still allows you to occasionally do some calculation or rendering!
Having more core would be useful to do a lot of calculation, or photo rendering (like 60-100% of the work week)
So more than 6 cores, for an occasional solicitation, it's like having a sports car, and staying in first gear...
That's my opinion...
EDIT: after the total budget to change some choices, such as instead of starting with the current generation, taking the previous one...