most probably x5687 & w3680 should work. If it wont work it wont brick the board. Just use Core i 7 to update the bios then all those cpus should work. probably x56xx & w36xx were incompatible with older bios version.
with w3680 you can oc with good air-cooler to 4.5 GHz but beyond that you may...
Correct but The Gigabyte seller is 100% for sample size of just 11 while The EVGA seller is 98.7% for sample size of 1191.
But actually main problem in Gagabyte X58 board Bios setting while overclocking is if you do not have uncore frequency in certain ratio in regards to cpu ratio your pc...
What happens if you press F1 to continue to boot in OS. Does the OS shows 24 GB or only 16 Gb.
Have you checked cleaning the ram slots and the Ram-sticks or swapping the Ram-sticks across the ram slots.
T3500/T5500/T7500 can all use aftermarket power supply without any issue. But in case of T5500 / T7500 if you have 2 CPUs , you will need a aftermarket PSU with 2 8pin EPS connectors ..... and of course the wattage of psu should the adequate to power your system.
AfterMarket PSU won't go into Dell Propriety System in case of T3600/T3610/T3620 ......... Unlike T3500 / T5500 / T7500.
But the problem with Dell Propriety PSU is that its a Multi-Rail PSU, unlike Aftermarket PSU which are mostly Single Rail
Depends upon what you do with your system. W3680 means $46 (from Aliexpress) investment. I use my system also for Video Editing with Da Vinci. So 12 Threads for editing $46 was worth investing. If you only game ..... then depending upon which games you play ....... evaluate if 4 cores is...