@Bugboijoe, honestly this is going to be a tough computer to upgrade.
Graphics cards: I know it's relatively new since, the processor came out in Q1 of 2015. But with a 180 watt power supply, I wouldn't even risk installing a 750 Ti. Therefore in order to simply install a graphics card, you'd need to upgrade the power supply, and since your current one is listed as "180 W SFF Bronze internal power supply", I strongly suspect that a standard ATX PSU won't fit. If my assumption is correct, then that eliminates a graphics upgrade.
CPU: The LGA1150 socket and Intel H81 does indeed support upgrading up to an i7-4790k (google query: intel h81 cpu support). The i3 4170 has a TDP of 54 watts, while the i7-4790k has a TDP of 88 watts. However, HP never made this line with the 4790k, probably because the PSU couldn't handle the extra 34 watts of power. While your computer is the HP Slimline 410-010, HP also released the HP Slimline 410-030, which had the i7-4790T, which had only a 45 watt TDP. Compared to Core i7-4790K there's an overall 16% performance decrease. SFF PCs offer the worse options to upgrade.
Sorry.