Radeon HD 4870 or 5770 to upgrade Mac Pro 1,1 2007 2.66 dual core?

2007 Mac Pro 1,1 2.66 dual core, 4GB RAM, running 10.6.8

I'm upgrading from a Radeon HD 2600 512MB with a very annoyingly noisy onboard fan (it sounds like an air compressor running in the distance). I am happy with its video performance.

I use my Mac for a bit of everything: dvd watching, game playing for Civ III/IV and SimCity4. Would like to play the new SimCity V when it comes out shortly. Doing some basic video editing of stuff I am extracting from videotape.

Does the Radeon HD 4870 have noise problems? I really don't want another card likely to become noisy at some point.

It looks like its just an equal swap for the performance I already have with the 2600 512MB card, or is there something improved about the 4870?

The 5770 looks very cool, but would its 1GB of memory go to waste on my old Mac Pro, or would it have noticeable improvement? I do read that the 5770 cards run quieter.

Help please. Need to make a decision soonest!

Any card with a fan is likely to become noisier over time (depending on it's environment and fan design). If you're happy with the existing card why not just replace the fan?

The only way to be sure that it's quiet is to get a passively cooled card but I'm not sure any of these are available for the Mac Pro with getting into flashing the firmware on normally non-compatible cards.

In Mac Pro days used an ATI Radeon HDD 4870, a 1GB flashed PC version, and it worked well and silently. If you can get a 5770 at a favourable price then go for it. Keep your eye on eBay Internationally. The 2600 did have a high failure rate.

Got a 5770, working, SimCity 4 issue

I got a 5770 replaced, one someone sold new out of a new Mac in which he upgraded to 5780's, I believe. Amazingly quiet! Everything seems to be working fine, though I noticed that at the same monitor resolution, the desktop got a little more crowded somehow. What's that mean? How could two different cards render 1440 x 900 differently?

The graphic performance of SimCity 4 has gotten notably WORSE with this card though. Not sure why that is either. Other video/graphics seem as good or better than before. I've only been testing this card out for the last half hour. I'm frustrated about the SimCity issue. I was not expecting it to play worse.

Any ideas what this is about or what I can do to fix it? Tweaking video settings for the game so far, but there aren't many.

The reason I didn't replace the fan on the old card is the seller of the computer gave me $180 to replace the card.