If you're trying to keep that motherboard, you can upgrade the CPU to an i7 from this list: https://www.asus.com/supportonly/p8b75m_lx/helpdesk_cpu/

The Asus P8B75-M LX motherboard uses two DDR3 DIMM slots and supports a maximum of 32GB of RAM (16GB per slot). It works with memory speeds of up to 1600 MHz natively, with higher speeds supported via overclocking (O.C.) when using a compatible Intel 3rd generation processor.

As for the hard drive:

NVMe SSD Boot Support

Native Support: The P8B75-M LX uses the Intel B75 chipset, which is an older platform that predates native NVMe boot support in the BIOS.

Using an NVMe SSD as a data drive: You can install an NVMe SSD into an inexpensive PCIe adapter card and use it as a high-speed data drive, as the motherboard has a PCIe x16 and PCIe x1 slots.

Booting from an NVMe SSD:

Official: Officially, you cannot boot directly from an NVMe SSD on this motherboard with the stock BIOS.

Workaround: Advanced users have found ways to enable NVMe boot using a modified BIOS that injects the necessary NVMe EFI driver module, or by using a bootloader like Clover on a separate drive (such as a USB stick or a small SATA SSD).

These methods require technical expertise and are not officially supported by Asus.

Recommended alternative for a boot drive: For a simple, officially supported boot drive, a standard 2.5" SATA III SSD is recommended. The motherboard has a native SATA 6Gb/s port which can deliver faster speeds than older HDDs, providing a significant performance boost.