Consultation. Equipment suitable for photometry of variable stars.

Hello. I am an amateur astronomer from Uruguay. I recently got the opportunity to invest some money in astronomical equipment. I am interested in buying a computer that allows me to perform photometry of variables to report to AAVSO. The camera is a Canon DSLR at prime focus T2i. I am in doubt as to the telescope. I have 5 possibilities and I want to show me as much as possible which would be suitable. Step by details:
1 - Celestron C5 w/ focal reducer
2 - Celestron C6 w/focal reducer
3 - Celestron Advanced Series C8-SGT (XLT) Computerized Telescope with focal reducer
4 - Celestron Omni XLT 150 R - 150mm f / 5 Refracting Telescope
5 - Astro Tech 8 "f / 4 Newtonian Imaging with correction of coma
All teams would equatorial mount go-to.
They are very different, but better to have to choose from.
From already thank you very much.
regards

Bernardo Pombo