I've worked an absolute ton on the accessibility of the game over the past few days which included supporting any resolution you can imagine with a ton of scaling options, and dramatically changing the way the game handles slowdown on slower computers.
With this work done, the game now plays MUCH better on computers lower spec than I originally had targeted, and I've just finished a round of quick testing on the slowest computer in my QA set (A Core Duo T2600 CPU at 2.2ghz on Windows XP, top-of-the-line 7 years ago!) and the game runs fine, so I'm officially changing the specs to a 2.0ghz CPU with no regards to the number of cores you have.
It may run fine on even slower configurations, but it's eventually just up to the player to how much they can tolerate playing a brand new game on a >7 year old machine. Then again, I finished Tomb Raider 2 on my 486 DX2/66 and the whole thing ran at about 3FPS, so some people are willing to put up with low framerates!
Anyway, just glad that more people with slower computers will be able to enjoy Black Annex now :D