I am a long time audiophile and have some experience in the wood shop. I would suggest a couple of things. First and foremost, if you are going to invest the time and money to build the cabinet for your speakers, make sure that the speakers are going to be a long term use item and are of the quality you want. Amps, pre-amps etc and their specs are very important, but the sound ultimately emanates from the speaker and each speaker is different. Infinity is a solid brand of speaker, but I am not familiar with the specific speaker you own. Make sure your cabinet can house both the speaker you own now and the speaker you may upgrade to later. You also want to avoid making the fit too tight, speakers vibrate and you don't want have them wedged against the sides of the cabinet, this will produce distortion to the sound.