I am looking at getting a Dell Optiplex 9010 mt that I can get for a good price it comes with only 4GB of memory and I want to upgrade it to 16GB I bought a memory kit for my older Dell Optiplex 780 that didn't work(wasn't supported) I am wondering if it will work on the newer Optiplex 9010, I bought 2 8GB kits of CORSAIR Vengeance LP 8GB (2 x 4GB)  DDR3 1600  CML8GX3M2A1600C9 that's now too late to return. The one I'm looking at comes with a 250GB hard drive and Intel Core i5-3470 3.2GHz. Windows 7 Pro (refurbished). I already have a 1TB Samsung SSD and a copy of Windows 10 Pro I can install. I plan to upgrade this computer as I can afford it but I can't use it with only 4GB of memory. I was told the newer Dells are not as fussy with memory upgrades as the older ones are(socket 775) is this true? The computer I got now has a Core 2 Quad Q9550 with 16GB memory and a 500GB Samsung SSD Windows 10 Pro I was told this newer Dell with the i5 will be about 80% faster then what I have now. I plan to order this computer when I get paid next but I would like to know what I'm getting into before I do. I also I can get a used i7 for this computer that's not too expensive would that be worth the upgrade?  I was looking at the Dell Optiplex 7010 mt for about $10 more but with 8GB memory same Intel i5, Windows 7 Pro and 250GB hard drive what's the difference between the 7010 and the 9010 version? should I go for the one with more memory or should I pick the Optiplex 9010 mt and just upgrade the memory?

Thanks for any help you can offer me.