If you enjoy building your own antenna, take a look at the GH2n and similar designs...
http://clients.teksavvy.com/~nickm/g..._5V7_12u8.html The Gray-Hoverman with NARODs have morphed the basic antenna from being a UHF only antenna into a remarkably good UHF/High-VHF combo... And it's quite compact.
A conventional store bought option would be an Antennacraft HBU series antenna. Or, as you have proposed, just add a Y5713 or Y10713 to your existing system. A simple UHF/VHF combiner could do the trick.
Another option is to toss the 10 dB amp... it's probably adding nearly the same amount of noise as gain (if it's like most of those I've seen). Replace it with a Channel Master CM-3410 adjacent to the antenna. With a PCTMPI1G power inserter, you can locate the power supply separate of the amplifier.
http://www.channelmasterstore.com/Am...p/pctmpi1g.htm
In some cases, placing an amplifier close to an antenna will isolate the effects of poor SWR, resulting in better performance. In this case, I suspect the SWR of the home made bow-tie antenna is quite high in the VHF band. Also, the CM-3410 has more gain with far less noise than the typical 10 dB 'boosters'.