I actually like using both like you do for stage makeup. The powder is suppose to "set" the liquid and make it last longer. (In fact, when I was taking stage makeup classes he said we're even to put powder over blush and lipstick. Though that powder he told us to use for that was colorless.) Ever since I used a liquid/cream foundation, then put a light coat of powder over it. I find it does last a smidge longer and the powder removes the shine from the liquid.

It may not be that you need a new foundation- but that your application may need to change. Firstly, your MAC foundation may to too thick for your skins changing needs. You can dilute your foundation by mixing it with your moisturizer. A think foundation tends to highlight problems in aging skin rather than camouflage them. Application makes all the difference in the world when applying any foundation. Using a sponge or your fingers makes it easier to apply too much product, and pushes into into your pores and fine lines. Try using a stippling technique with a dual fiber brush. Here is a video to show the technique http://www.youtube.com/watch?v=3aoXfB4cVlE MAC makes a stippling brush, but its expensive. Sonia Kashuk makes a great dupe that you can find at Target.

Powder/mineral foundations are generally the easiest to work with, and do not settle into pores and and fine lines the same way that liquid can. Powders however, do not offer as as much coverage as liquids. But applying a good concealer (MAC's Studio Fix is great) to trouble spots prior to applying your foundation powder will help this. One of the best mineral foundations I've tried (and I've tried a lot!) is by CoastalScents.com. It is their Silk Cover foundation. It can't be beat for any price. What's great is you can order samples before you buy the full size. Minerals are great because you don't have to have a perfect skin match in the same way you have to with liquids. Coastal scents also makes the best foundation brush for applying powder foundations. Here are the links to the foundation and the brush http://www.coastalscents.com/cfwebstore/index.cfm/category/108/silk-cover-mineral-foundation.cfm http://www.coastalscents.com/cfwebstore/index.cfm/product/1483_37/synthetic-wide-buffer-brush.cfm

But great looking skin is part of great skincare. I love the Clarisonic Facial Brush (Sephora) , it totally transformed my skin!!! I can't live without it. But it is expensive... Try LUSH Ocean Salt scrub (LUSH kiosks are at most Macy's) on your face every other day, and use Korres 24 Hour Wild Rose Moisturizer (Sephora). It is incredible!!!! and it doubles as a makeup primer!

Hope that helps!