page with specifications
http://support.hp.com/za-en/document/c04918469
ram need to be: Two 240-pin DDR3 DIMM sockets, Supports the following: PC3-12800 (DDR3-1600)and PC3-10600 (DDR3-1333)
Supports 1 GB, 2 GB, 4 GB and 8 GB DIMMs, Supports up to 4 GB on 32-bit systems
the power supply is not an TAX PSU but a 300 W uATX aPFC internal power supply
uATX is the format you need to look for when replacing it.
I see no issue using the 1050 Ti video card inside this PC, just make sure you change PSU first