Im sure the Picatinny style Talley rings are steel. Their lightweight ringmount is alloy but most of the rings and bases Talley makes are steel. If you want to call Talley and ask this is their phone number Phone: (803) 854-5700.
From what you are telling me I would say that the 16x42MQ is probably a good choice for you. I find that the Mil Quad reticle is what I prefer in that scope where in the 6x I tend to prefer the mil dot and with a 10x its a toss up either is fine, but at higher powers I believe the Mil Quad is a great benefit and I prefer the 1/10 mil adjustments to 1/4 moa because the reticle and the adjustments are in the same type of increment. The military has used the 10x but the construction quality is the same throughtout the line. You should realize that the military also uses some very high magnification optics not just 10x .
6x has a 7mm exit eye pupil so it is a very bright scope in low light
10x has a 4.2mm exit eye pupil so useable in twilight but not ideal
12x has a 3.5mm exit eye pupil so not as bright as a 10 but brighter than a 16x
16x has a 2.6mm exit eye pupil so not ideal in low light
20x has a 2.1mm exit eye pupil so this willl look rather grey in twilight
As the power goes up you win in some areas and loose in others
With the more expensive group of scopes the 10x HD the 3-9 etc there are differences the most noticable to you would be that these scopes have exceptionally good glass and are built extremely tough. The 10x HD was also built to current military specs and it is a significant improvement over the entire original group of scopes. The 3-9 is probably the bigest bargain in the entire line because so many people want that magnification.
This HD version of the 10x is the latest military version, Ive had one but I moved up to the 5-20x50 HD which I like better and find that the variable is a huge advantage: