Really worth to OC the Vapor-x 7770 ghz Pre OC edition?

Take it slowly.
Increase core clock by 10MHz and run afterburner. Keep eyes on temps and artifact count (it has one right?). Try to stay under 75-80'C. You can set fans to 100% but it is not needed.
If you overclock too much and card crashes it will revert last change (or back to default) in clocks speed. It is not that easy to burn hardware nowadays. As long as you do not play with voltage you are safe.

PS. That card looks nice!
Overclocking the SAPPHIRE Vapor-X HD 7770 GHz EDITION OC was a piece of cake. I have used MSI AFTER BURNER to push the SAPPHIRE card as far as i could, and i managed to hit up to 1225 MHz (Core) / 1500 MHz (Memory), but due to some stability issues at these high clocks i lowered my settings to 1200 MHz (Core) and 1475 MHz (Memory). These are what worked for me that does not mean they will for you. No fan settings or voltage settings needed to be adjusted. These settings were just easily set through the overclocking utility while i was running Unigine Heaven 3.0 in the background to check for stability.

I've never used trixx so it would not be fair for me to say.I think you should use which ever your comfortable with

Update to the latest beta driver from AMD. Overclock with Afterburner. You will always run the risk of frying your card, but you can largely avoid that by increasing clock speeds little by little. Run a benchmark test after every overclock, you will know when to stop when you get graphic anomalies, artifacting.

Or you could look around the web for what most people managed to get with a 7770.

What do we need?
One of the best tools for overclocking NVIDIA and ATI videocards is our own AfterBurner which will work with 90% of the graphics cards out there. We can really recommend it, download here. http://download1.msi.com/files/downloads/uti_exe/vga/MSIAfterburnerSetup231.zip

Where should we go?
Overclocking: By increasing the frequency of the videocard's memory and GPU, we can make the videocard increase its calculation clock cycles per second. It sounds hard, but it really can be done in less than a few minutes. I always tend to recommend to novice users and beginners, to not increase the frequency any higher than 5% on the core and memory clock. Example: If your card runs at 600 MHz (which is pretty common these days) then I suggest that you don't increase the frequency any higher than 30 to 50 MHz.

More advanced users push the frequency often way higher. Usually when your 3D graphics start to show artifacts such as white dots ("snow"), you should back down 10-15 MHz and leave it at that. Usually when you are overclocking too hard, it'll start to show artifacts, empty polygons or it will even freeze. Carefully find that limit and then back down at least 20 MHz from the moment you notice an artifact. Look carefully and observe well. I also recommend you run these two programs to make sure your oc is stable
Unigine 'Heaven' DX11 Benchmark
http://www.techpowerup.com/downloads/2111/Unigine_Heaven_DX11_Benchmark_3.0.htm

You should set the Resolution to your monitors maximum supported and/or the resolution you plan to use in the majority of games.

Be sure that you remember to click the 'Benchmark' button in the top-left corner of the screen after the program loads to actually start the Benchmark. I'd also suggest turning off the sound by clicking the button on the top-left menu bar. Also, if you alt-tab out of Heaven, you will need to close it completely after that to get a real score. If you notice that your score suddenly dropped by 10 or more FPS, then your card is probably stuck in 2d mode. To fix this, first try restarting your computer.

To stop the benchmark at any time, press the esc key and then click quit.

3DMark 11
http://www.3dmark.com/3dmark11/download/

If you're using the free version then each time you open 3dMark11 you will need to click the "upgrade later" button. Switch the preset to 'Performance' if it's not already there and switch it to run only the Benchmark Tests in Centered Mode.

The esc key can be used at any point during the benchmark to end it prematurely.

All in all... enjoy and take your time.

Your welcome.You have a nice day as well.