So their bracket just puts both horns in the front of the radiator?
Also, how necessary is the harness? What would I have to buy/modify if I didn't get the harness?
You'd think they'd make a combo pack with both, $30 seems a bit steep for that bracket and $60 total is more than the horns.
If you want to mount them symmetrically, there are no factory holes to use. So you have 4 choices:
1) Mount them in the OEM position. This is a bad idea since one of them will be deep behind the passenger-side headlight.
2) Measure and drill. This is a bad idea, at least for me, for many reasons.
3) Custom/Macgyver style bracket. That may take a while... took me about an hour to get it in the right spot so the horns wouldn't be in the way of the grille. For aesthetics, I wrapped the bracket in black electrical tape. That took a couple of tries.
4) Subimods bracket. From what I can tell this is a nicely powder-coated bracket and the spacing/sizing is just right. Pretty much plug and play. I’m actually thinking about ordering it and replacing my custom bracket. Not sure. This one isn’t as much of a MUST as the harness.
Placing the horns in front of the grille looks to be accepted practice. I wondered about decreased radiator performance, but I don't do any towing and the surface area covered by the horns is not large.
Also regarding the harness… I too was on the fence. Hard to justify spending that kind of money on a part that's really an amalgamation of easily available parts. However unless you have all the requisite pieces and if you do that math, add in the time it takes to make a custom harness, you'll agree that the harness is well worth it. Also, the way they put the harness together is the way I'd do it, so that would bring my cost up. All wires are wrapped, terminals are finished in heat-shrink tubing, and the inline-fuse holder includes a fuse and appears to be waterproof. Best of all the wire lengths are perfect for the Outback. In case you want to go it alone, you'll need quite a few things...
1) Female terminal x 4... two horns, two terminals each. Example:
http://ecx.images-amazon.com/images/I/31M0Ijt-dNL._AA115_.jpg
2) Male spade x 1 This goes to the factory OEM plug which runs from the steering wheel and acts as the positive switch for the relay. See diagram 2b of your hella install doc. Example:
http://ecx.images-amazon.com/images/I/31ni52nTPbL._AA115_.jpg
3) Ring terminal x 2 one large for the Positive battery terminal and one smaller for the Negative terminal. Example:
http://ecx.images-amazon.com/images/I/41qrzWrZHXL._AA160_.jpg
4) Relay socket x 1 This is not my area of expertise and I would have been frustrated wiring this up correctly so another plus for subimods. Example:
http://ecx.images-amazon.com/images/I/21qjzhUuEiL._SL500_AA300_.jpg
5) Relay x 1 The Supertones come with a 4-pin relay, Subimods recommends a 5-pin. They include it with every harness purchase (if your order and there is no 5-pin, contact them, they'll ship one to you). This is also an area I don’t know much about and would be nervous getting into. Example:
http://ecx.images-amazon.com/images/I/418wJOPFKYL._SL500_AA300_.jpg
6) In-line fuse holder x1 Example:
http://ecx.images-amazon.com/images/I/21GFVc+hSFL._AA160_.jpg
7) 20-amp blade fuse x 1 Example:
http://ecx.images-amazon.com/images/I/51cex91LkmL._AA160_.jpg
8) 5 or more feet of wire wrap Example:
http://ecx.images-amazon.com/images/I/31u63XnoyhL._AA160_.jpg
9) Wire… not even sure what gauge would work well for the voltage/amperage.
Again, unless you have these things lying around, you should save yourself the time, money, and guessing/frustration and get the subimods harness. I'm glad I did.
Hope this helps.