I found a good deal for a T5820 on an online flea market. This model is still on sale and is one of the costy desktop models by Dell. Even though it's 4 year-old specs, let's see if it's worth the money.
0:00 Unbox
0:17 Exterior
2:17 Internal & clean up
7:16 Things I like
9:01 Things I don't like
11:39 GPU choice
13:52 Performance
16:07 Outro
Where did I buy it from:
https://jp.mercari.com/item/m61337236964
Benchmark result:
https://www.userbenchmark.com/UserRun/59995183