You get what you pay for. IMHO Hifonics are mainstream, China low end build quality and don't sound that great. Hifonics had some good amps back in the 90's I think. A $300 budget is really tight and you may not be happy with your purchase. Here is my suggestion to you:
Image Dynamics IDQ 10" (under $150 depending on where you shop)
Sundown Audio SAX100.2 ($240 @ Soundsolutionsaudio.com)
Yes these are made in China, but they have a much better reputation for SQ, reliability, build quality, etc etc etc.
I really urge you to consider building the box yourself or paying someone who has the knowledge. It will be money/time well worth it. A rule of sound quality is 70% install. If you are sticking with sound quality/accuracy go with a sealed enclosure. A properly ported enclosure will give you about 3db more and may hit lower frequencies.
Rear fill is completely not needed, especially on a budget. Spend that money on better front stage and amp(s). CDT makes fantastic components and coaxils with really resonable prices.