I would strongly recommend that you hit up eBay for this purchase. You can often pick up any of the brands you listed for well under $1,000. eBay buyer protection will cover your shipping if there is something that is not working properly. I've picked up numerous amplifiers over the years that I use on installation jobs from eBay at fantastic value.
So, while you can pick up the Niles SI-1230 right now for $470 (shipped)...
If you really do have more budget, then you can go with something more like the Sonance 1250...
While there are a number of people that say 'AS-IS' or 'NO-WARRANTY', if they don't list the product as 'FOR PARTS', then they are required to provide you with a fully working 'used' item. eBay will protect you even if the original seller claims that they 'said it was as-is'. I've had similar occur, and eBay protected me when the seller was being a tool. I should say, this happens exceedingly rarely to me and I've been buying from eBay for ages.
Now, what I really would recommend...
Get a 1230 or 1235 amplifier that has a 'BUS-IN' connection so that you aren't splitting your inputs, but use a common feed to all.
Next, make sure that the channels can all be bridged.
Now, just get one! If you go outside and find that you are yearning for a bit more power, go out and pick up a SECOND 1230/1235 amplifier. Set all of the channels to 'bridge' mode, and you should be pushing 60+ watts out to all the speakers.
This solution costs you the least right now and gives you the opportunity to upgrade down the road if you want more power outdoors.
This listing is similar to the Niles 1230, and would probably be about where I would start:
It is bridgeable and has bus-in and bus-out connections for multiple amps to share a source. It even provides a second bus (aux) which allows for a second source if necessary.