DELL OptiPlex 780 - tune up memory and CPU

Hi everyone
I want to tune up old DELL OptiPlex 780.

Documentation:
https://dl.dell.com/manuals/all-prod...nual_en-us.pdf

1. Memory:
As per documentation, maximum possible RAM capacity is 16 GB (4x 4GB).

Question: what should I look/ask for? Eg:
- DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
- DDR3 SDRAM (non-ECC memory only)

2. CPU:
Question: How can I find out what would be the fastest CPU that this motherboard supports?

lshw output:
Code: *-cpu
description: CPU
product: Intel(R) Core(TM)2 Duo CPU E7500 @ 2.93GHz
vendor: Intel Corp.
physical id: 400
bus info: cpu@0
version: 6.23.10
slot: CPU
size: 2933MHz
width: 64 bits
clock: 1066MHz
capabilities: lm fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx x86-64 constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm pti tpr_shadow vnmi flexpriority vpid dtherm
configuration: cores=2 enabledcores=2 microcode=2571 threads=2
*-cache:0
description: L1 cache
physical id: 700
size: 128KiB
capacity: 128KiB
capabilities: internal write-back unified
configuration: level=1
*-cache:1
description: L2 cache
physical id: 701
size: 3MiB
capacity: 3MiB
capabilities: internal varies unified
configuration: level=2
*-memory
description: System Memory
physical id: 1000
slot: System board or motherboard
size: 8GiB
*-bank:0
description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
product: M378B5673FH0-CF8
vendor: Samsung
physical id: 0
serial: 86B42431
slot: DIMM_1
size: 2GiB
width: 64 bits
clock: 1066MHz (0.9ns)
*-bank:1
description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
product: M378B5673FH0-CF8
vendor: Samsung
physical id: 1
serial: 86B42356
slot: DIMM_3
size: 2GiB
width: 64 bits
clock: 1066MHz (0.9ns)
*-bank:2
description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
product: M378B5673FH0-CF8
vendor: Samsung
physical id: 2
serial: 86B4235E
slot: DIMM_2
size: 2GiB
width: 64 bits
clock: 1066MHz (0.9ns)
*-bank:3
description: DIMM DDR3 Synchronous 1066 MHz (0.9 ns)
product: M378B5673FH0-CF8
vendor: Samsung
physical id: 3
serial: 86B42358
slot: DIMM_4
size: 2GiB
width: 64 bits
clock: 1066MHz (0.9ns)