Being both the family tech, and a Geeksquad employee, I have a fair bit of experience in dealing with wireless systems. Unfortunately, there are a large amount of variables which can play into the quality of service of your wireless network. Some things you won't have control over, such as building materials of your house, external interference from other wireless networks in close proximity, and other wireless devices which operate on the same 2.4 Ghz frequency. Some things you will have control over, such as router placement, antennae positioning, and the wireless channel you are using.

While repeaters can work, in my experience getting them set up is the biggest obstacle. Once set up, however, they can be fairly effective, depending on how many networks there are around you. The best way to get the most from your repeater is to get it set up while plugged into the router via ethernet. Then, using a laptop with a program such as netstumbler, find the sweet spot in your house for it's placement. More often than not, you may need an extension cord and some creative placement to hide it. Regarding wireless channels, in the US (for what reason I forget) only three of the given eleven channels are actually separate. Channels 1, 6, and 11 do not overlap one another, but any channels in between will. Finding which of these three channels has the fewest other networks on it is your best chance at increasing signal strength and quality.

Generally speaking, the easiest and cheapest way of improving your speed and quality is by using a better/more powerful router and avoiding extra devices. You may even want to try using a powerful wireless N router. However, that will be a costly upgrade as you will need to replace the wireless cards in your computers to receive the full benefit. Also, if it turns out you do have many other wireless networks in your area, going with a dual-band wireless N router may be a good choice as well.

I hope I have been somewhat helpful to your situation. Unfortunately, the best way to give good wireless advice is by actually surveying the situation first-hand.