Don't buy things from Crutchfield. They tend to be expensive... although the stuff itself is good. Only go there if they have a special or a deal. Sonicelectronix is usually cheaper.
That Alpine is too expensive. I've thought about buying it before. You can get a Pioneer that puts out double that wattage for the same price.
As far as Hifonics, they're usually not CEA-2006 compliant. The one you posted is actually compliant, so I would give it a shot. I had an old Crunch amp (before CEA-2006) and it would push these old school Audiobahns with ease. Crunch and Hifonics are made by the same people, so I would trust em, but be wary of the ratings. I bought a newer crunch amp thinking it would be good but the rating was off. I was also a sound newbie still at the time, so I mistook 200watts total for RMS. I didn't realize what happened until after the fact.
Hifonics is a better line than crunch though, so I would keep it as a back up, depending on what you want to use for speakers.
Considering your budget is $150, here's what I would buy in that price range. Mind you, I listen to rap music and require loud speakers due to my car being a convertible.
Jensen Power 760.4 - $70
http://www.sonicelectronix.com/item_...wer-760.4.html
Jensen is not a bad brand, but it is an entry level brand, similar to your dual head unit. 75 watts x 4 for $70 is not a bad price at all. It would also handle most run of the mill speakers that are usually sold in between $50 and $80 bucks.
Sony XM-ZR704. - $120
http://www.sonicelectronix.com/item_...-XM-ZR704.html
This amp is 70x4 @4 ohms. Nothing too fancy, but better than 50 watts x 4 and those 70 watts are enough to power most mid level speakers, which usually are between 60 watts and 80 watts. Only the higher end speakers are actually 100 watts and over.
Pioneer GM-D8604 (no relation to General Motors). $150
http://www.ebay.com/itm/Pioneer-GM-D...e27b &vxp=mtr
I'm as frugal as they come, so I will always look for the best price no matter what. Here's the sonic link so you can see the specs.
http://www.sonicelectronix.com/item_...-GM-D8604.html
Not a bad amp overall, it's 100 watts x 4 and is basically the same price as the Alpine and Infinity, but with more power. I personally don't like Pioneer, but it's very popular and many folks have good things to say about em.
With all of this said, if I was you, this is what I would do...
Pioneer Amp.
http://www.ebay.com/itm/Pioneer-GM-D...e27b &vxp=mtr
Alpine 6.5 - $72 for component, $60 for normal 2way. I would convert the front doors to 6.5 from 4x6. It's a relatively simple procedure, I wish I had pictures, but you need to drill holes in the door to mount it. I would also get component speakers to have a tweeter in the sail panel. 80 watts rms.
http://www.ebay.com/itm/ALPINE-SPS-6...item4d1cd1983b
Info.
http://www.sonicelectronix.com/item_...-SPS-610C.html
http://www.ebay.com/itm/ALPINE-SPS-6...item1e87829448
Info.
http://www.sonicelectronix.com/item_...e-SPS-610.html
Alpine 6x9 (for the rear shelf) - $50 It's an 80 watt speaker, drops in the rear shelf. The stock speaker is fully clipped on, you don't have to screw anything in BUT you have to take off the side of the seats and the C pillar trim to get to the rear shelf. It helps if you take out the bottom seat cushion.
http://www.ebay.com/itm/Alpine-SPE-6...item461e19fd7d
Info.
http://www.sonicelectronix.com/item_...-SPE-6090.html
Should you want to stick to 4x6... Sonic is the cheapest.
http://www.sonicelectronix.com/item_...64-KSC464.html