Should I upgrade to A77 or stick to my A550??

Hi everyone,

I've been using the A550 for a couple of years and I really enjoy it. I have 4 lenses: Sony 70-300 , kit lense 18-70 (i think), Sigma 70mm Macro and Sony 50mm 1.4

If I'm not mistaking, all four lenses can be mounted onto the A77. I've read about the pros and cons of the A77, which all in all seems to be real good value for money. The video seems to be capable of great things (even documentary filmmaking) which can be great fun.

I'm a bit afraid the 24mp sensor and the transluscent mirror of the A77 will make it difficult to take pics in low light. How does that compare to the A550?

Is it a really subsantial jump in the quality of the pictures?

I do a lot of portraits and want to start getting into landscapes.

Thanks for your help!