Intel SR2612URR (2U, Dual LGA1366, 12bay HS) - Lower Heat and Power Consumption with CPU swap


May 15, 2019
First off, I apologize for posting about such ancient hardware in this forum, but hopefully it won't be much

The Background:

I have an old Intel SR2612URR 2U/12bay hotswap chassis. It's complete, unmolested and in as-sold trim.
Current CPUs are a pair of E5620 (lowest bin 4c/8t 80W 32nm Westmere) and run hotter than I like/want.

I have a pair of L5638 6c/12t 60W CPUs that I plan to throw in, to lower cooling requirements and energy from the wall.
I also found 2 possible model candidates to purchase if needed - both being an upgrade/downgrade at the same time.
Both are the respective 'flagship' in their TDP rating/ I would assume the best efficiency per clock.

My goal is to lower heat, lower cooling/power requirements/consumption...and perhaps unplug a fan or 2.

My Question(s):

Does it make sense to assume that the best (high) clocked model at a given TDP will be the most power efficient ?
Considering an aged platform, yet low price of better CPUs (for my goals), is it worth even spending the $10-$20 ?
Am I wasting time trying to preserve every last clock and power efficiency number for nothing ?

With my goals considered, which option seems the most reasonable ?

1) $10 to lower clocks ~10%, same core/thread count, 80W TDP vs. 160W (see L5630 below).

2) $20 to lower clocks ~5%, increase 8c/16t to 12c/24t, 120W TDP vs. 160W (see L5640 below).

3) Not waste time or money. Run L5638. Big clock decrease, increase from 8c/16t to 12c/24t, 120W TDP vs. 160W
(still saves power, clocks are negligible since it's all old garbage anyway).
Xeon E5620 - 4c/8t - 2.40/2.66 Ghz - 80W (Currently installed, low end bin for TDP, run hotter than I like)
Xeon L5630 - 4c/8t - 2.13/2.40 Ghz - 40W (Best 32nm 40W 4c/8t Westmere) $10/pair inc.shipping.
Xeon L5638 - 6c/12t - 2.00/2.40 Ghz - 60W (I already own a spare pair)
Xeon L5640 - 6c/12t - 2.26/2.80 Ghz - 60W (Best 32nm 60W 6c/12t Westmere) $20/pair inc.shipping.
As always, thanks in advance.