I have to agree with every one who has tried to steer you away from a 2-way with a 15" woofer and a 1" tweeter. It may be OK for a PA loudspeaker, but is not at all good for a hifi speaker. Under the right conditions, an 8" woofer is the biggest woofer that can be successfully crossed with a 1" tweeter in a 2-way design. To get an idea about what is going on here, read the article titled "Choosing the Crossover Frequency"
http://www.speakerbuilder.net/web_files/Articles/xover article/xpointmain.htm
This may seem like too much reading and too little direct advice. True. Read and learn if you want to be able to recognize which designs may be good and which are obviously poor. Its my guess that you're probably better off following some one else's successful recipe. The kits available from Madisound or Parts Express are not bad, but a few of them can be expensive.
That is why I suggested designs that have been around long enough to generate good feedback from people who have actually built them, designs that fit your price range, and designs that are written and illustrated well enough so that new builders can easily follow. What good is an excellent design, if it's write up lacks enough detail for you to follow? The following websites are by good speaker designers who I think fit the bill. Except for Wayne J, they all will answer your email questions. I added his site because he has good designs that aim for lower prices, and some of his articles (like the one I mentioned above) explain things very well.
Lou C
http://www.lonesaguaro.com/speakers/
Dennis Murphy
http://murphyblaster.com/content.php?f=main.html
Roman Bednareck
http://www.rjbaudio.com/
Wayne J
http://www.speakerbuilder.net/web_files/default.htm
What kind of speakers do you really want? Are they for music listening or home theater, or both? You may not know that answer in any detail now. I can only offer suggestions based on what I
think you may like and what price you want to pay. I warn you that I haven't heard most of these designs. They may look good on paper, but unless I've heard them, I can't say if like their sound or not. And the real question is what will you like.
From your initial post, it sounds like you want lots of bass and you don't want to spend more than $500 for a pair of floor-standing speakers. There are more than one way to get that. The Jubilee, Veritas, and Dayton 8 MTM designs should all meet those minimal requirements.
Another way, as WmAx and others suggested, is to use a simpler 2-way design, typically with a 6.5" or smaller midwoofer and a 1" tweeter, or the so called MTM variation, which is two midwoofers one tweeter with a 2-way crossover. Build these in a bookshelf type cabinet instead of a floor-standing tower. To get more bass, add a 10" or 12" woofer in a separate cabinet. Often these are powered by a built-in amp. This type of set up can deliver very satisfying bass, and will not sacrifice any midrange response that sometimes is missing in some larger floorstanding models that are designed to emphasize bass. An added advantage is that it is easier and less expensive to build smaller 2-way or MTM cabinets and separate woofer cabinets, and you can build them in stages rather than all at once.
