Starcruzzer, welcome to the site! If you haven't already found them, there are lots of excellent articles on gear selection and those wanting a lightweight pack listed in the left-hand column of http://www.backpacking.net/, the home page of this site. If you want a lightweight pack, please read through these articles before you do any more gear shopping! The gear lists there are especially helpful. After that reading, your next purchase should be a postage or kitchen scale that weighs to the nearest 0.1 ounce. Then weigh each gear item and set up a spreadsheet so you can see what the total weighs. (The spreadsheet is also a great checklist--I print mine off every time I go out!)

We really can't give you much advice about your gear unless you provide more detail in your profile--that's what it's for! Where do you live, where will you be backpacking, are you solo or part of a group, what weather conditions do you expect? The other information we need is the weight of each of your gear items (which is why you need the scale).

As stated above, unless your winters are really mild and your summers are cool, you do not want to try for a single set of "four season" gear. Clothing, most of it, is OK--just add more layers in winter. Sleeping bag, probably not. Tent, probably not. I have only one set of gear (with a few items added for "shoulder season" and for trips to the high Rockies where it can snow any time), but (1) I live in a mild climate (western Oregon) and (2) I don't go out overnight from mid-October through March.

Just one note on the "expedition" and "midweight" long underwear (known as "baselayer" these days). The purpose of the layer next to your skin is primarily to wick away moisture from your skin. A lightweight baselayer is actually far better for this purpose, regardless of weather. Other materials, such as synthetic fill or fleece, do a better job of insulating. I've gone the heavy baselayer route and it did not keep me any warmer, just made it harder to keep dry!

Please do the reading I suggested, give us the information we requested and add the weights (to save time, just edit your original post and make another post in this thread that you have added the weights). Then come back and we can give you specific advice! We'd love to help you, but we need more information!