A couple of things to think about, saying 105 or Ultegra is meaningless, if your building a bike, you need to know the generation, i.e. 5500/5600/5700/5800 for 105 as there are many variations and incompatibilities within these, for rims, if it's Shimano, as a general rule, unless you have a Shimano hub, and possibly proprietary spokes, it ain't going to happen (Shimano rims are sold as a wheel, buying them is only really done if you have wrecked the rim, and often they are priced to be cheaper to just buy a complete new wheel, especially at the lower end).

You mention 2x8/9, realistically, if your looking at that level, it's going to be cheaper to jut buy a bike (and it is at most levels, unless you really know what you doing/have access to heavily discounted part (i.e. working at a LBS) or are patient on waiting for bargains.