What hardware would you recommend for a virtual lab?

Question

Iron

In short, my home PC no longer pulls out all my "experiments". Main bottleneck: CPU and RAM.
Since I take for my money + not for production, I want as much as possible for the least possible money. I look mainly at used dual-processor servers from foreign flea markets.
Therefore, a few questions:

1. Does it even make sense to take "fresh" hardware (socket 2011/2011-3) for a lot of money, when there are components of past generations cheap as dirt (xeon 5500/5600, DDR3 RAM, SAS2 controllers, ancient 10G network adapters)?
   
2. Will the same xeon 5500/5600 be enough for another 5 years? In terms of power, everything is fine with them, but for some reason I stopped following the fresh "features" of the same processors (similar to vt-x, vt-d at one time)
   
3. Which manufacturer should you pay attention to? Dell, HP, or just give up and take Supermicro? It is clear that there will be no support, and even more so drivers / certification. But at the same Supermicro and Dell, you can always find old firmware / bios's in the public domain, and that's it. HP has a bit of a hard time with this after the split. In addition, Dell certified its r610 / r710 for the previous (2012R2) version of Windows Server, which makes them somewhat more relevant than their counterparts.
   
4. And finally, perhaps someone will advise specific places where you can get hold of all this? I know about Ebay, but shipping a server from the USA, especially 2U, will be more expensive than the server itself
   

Basically, it is planned to drive Hyper-V and a dozen virtual machines on the server. Compatibility with ESXi (especially RAID controllers) will be a huge plus. In terms of resources, approximately 8+ cores are obtained and from 48 GB of RAM. There are potentially no problems with the storage: I plan to give an already existing array from SSD via iSCSI from my home PC.

Answer 1

Will the same xeon 5500/5600 be enough

They may be enough, but I once took a DELL T610, and its electricity consumption is quite significant compared to more recent models. So it might make sense to overpay for the equipment a little, but save on food.
When I experimented with the T610, I found that almost all Dell RAID cards from DELL (for this series) do not support drives larger than 2TB. In my opinion, only PERC H710 supports. Well, the SAS / SATA bus bandwidth is also not the fastest for an SSD.
Now I took a DELL T130: 1 Xeon 4/8 cores, 64GB DDR4, - generally satisfied, but the SATA controller, which on the motherboard is a little buggy with ESXI (support said that ESXI is not supported with it, and if I want ESXI, then you need to take a separate RAID card.By the way, Windows Server is officially supported even with a parent controller). But I had slightly different goals, I took an LSI HBA card for myself - a couple of problems also got out there, but in general it works for my purposes.
If anything - I'm in the USA