First of all, is it important to upgrade? Is this PSU fine, great, or oh my God replace that!
One of my main things I'm also looking into with an upgrade is that the ambient temperature in the room is relatively high and reduces the amount I can overclock, would getting a PSU that is ~10% higher efficiency (>80 on current to 90%) allow me CPU to run cooler? Currently with an AMD Phenom II X4 955 overclocked from 3.2 to 3.6 I get about 39c idle and 48c under average load (higher if played Crysis 3 or similar games for extended periods but 48c is average for most gaming for me). Also, in addition to higher efficiency would I potentially get better temps due to better cable management as the new PSU being modular.
No. Your PSU is not a reputed brand, but has good review and since it works fine why change it? It is a decent PSU. Its not worth shelling out money for a new one. A new PSU will not make your CPU cooler either. A modular PSU is nice, but not worth replacing a good, working PSU for. Your temps are very good too, there's nothing to worry about on that front.
The things to look out for over time are drops in cpu scores while running 3dmark benchmarks (run it, take a note of your CPU score and check it every 6 months) and hanging whilst loading windows or freezing in games. If the pc does any of these things you need to check it out by borrowing another psu.
Dont spend money yet.