DJ Rob,
Well, my first impression of the difference between a 90 cm and a 1.2 M dish would be to say that you won't pick up very many more channels than you already have. Especially in your location. Many of the sats available to your area in the Ku-Band don't even require a dish of 90 cm in size. I stepped up from a 75 cm to a 1.2 M dish and in all honesty, there were very few sats or channels which were gained. It barely helped with a couple of borderline signal channels. I had hoped that the RTV channels on 83W would have come out smelling like roses, but there was only a slight improvement. The best improvement you will find is the reduction of rain fade affects. So, I wouldn't go this route in YOUR specific case. If you lived much further north or across the northern border, I might have a slightly different view.
A C-Band dish would be an excellent addition to what you already have. However, as Anole stated, you can very often and very easily pick up a used BUD for nothing or next to nothing. So why spend any money in this direction if it is not necessary. You might plunk down a little for the controller if needed.
Now, getting to the AZBox, I think I will have to go along with Anole once again. However, I would stipulate that you opt for the Premium model. This is more expensive, obviously, but you gain some amenities that I have found that I would not like to be without now that I have enjoyed them. These are:
1] Built-in WiFi! Fantastic!
2] External P.S. (which reduces the heat within the AZBox itself).
3] Internal HDD add-on capability. Works great! Especially with an Eco-HDD or Green Friendly HDD. I use a 1TB Samsung and it is fantastic. Quiet as a "dead" mouse and extremely cool operation! I am not exaggerating in the least when I say that it is QUIET.
4] The quirks and bugs are fast being corrected and new features are being added. With the exceptions of BLIND SCAN and dual satellite tuner support at this time, you will be amazed that this box is as inexpensive as it is.
The AZBox gets my vote as I am already trying to buy a second one. I mentioned this a while back, but there was a problem with the supplier to the retailer. They sent him a shipment of Elites instead of Premiums, so I have to wait until he gets more Premiums in. This availability might be a drawback to you if you want one very soon.
Since you requested opinions, I presented mine and with some information to support my reasoning as well. But, to be honest, there are a LOT of things that I would like to buy, period. So I understand the dilemna of deciding. If you do buy the AZBox, I do believe that you will be thrilled quite considerably. I know that I am and I have tried many other boxes searching for one that suits my needs and I think that this AZBox is just it. Just be forewarned that a lot of special considerations go into setting this box up. It isn't a plug-and-play box and requires the support of a PC to really utilize it fully. You might cuss at it and possibly become a little frustrated at first, but it is WELL worth it overall and it is definitely getting better with each new image release. (Image is the term for the firmware in Linux OS boxes).
Hope that my opinions and information gives you a good bone to chew on! Good luck and best wishes in your decision.
RADAR