Keep in mind with titanium you can't really repolish it to well....I am not sure on the finish over time, most titanium stuff I own has sort of 'tarnished' for lack of a better term....stainless, silver, gold, etc can easily be polished.
With diamonds I know quite a bit, the first thing is going to be figuring out what shape you want...each has it's pluses and minuses.
For $1000-2000 you can buy some nice diamonds in the 3/8 to 3/4 carat range.
diamondtalk.com is a great site.
The thing is the 4'C's are really worthless if you don't have the other aspects of the stone....it's like a nicely spec'ed gaming box full of third rate hardware with flaky drivers.
I am looking for a 5/8 round....I wanted a 3/4, she wanted only a 1/2...she thinks the larger diamonds makes her hands look old....she'd like a nice watch with the difference...
For color it's going to depend on a yellow or white gold/platinum setting...if you are going to set the diamond in yellow, going to D/E/F in color is sort of a waste if 'looks' are what you want (and should be in my opinion since a diamond is a terrible investment really).
Then clarity, anything better than SI2 in smaller stones makes it hard to find flaws (they should not be visible without a 10x loupe when viewed from the top) and I'd recommend SI1/VS2 or better.
There are other important specs, crown height/angle, pavillion, gridle, culet, symmetry, polish, etc.....
With rounds you can get what is called a 'hearts and arrows' cut which refers to the way light is measured in the stone....these = ideal cuts, but you can still have 'problems'.
Department stores and Mall jewelers will have stones roughly 50-100% more in cost than a private jeweler....do not pay attention to 'Appraised Values'. My last diamond 'appraised' at $5k-7k in a jewelry shop but I bought if for $2k a few years ago. (the lower figure being a Mayors type store and the higher being Tiffany and Co.)