What level should I be before going through the Omega 4 Relay

I have all the squad members that come with the standard game and the mercenary from one of the DLCs. They are all loyal. I'm currently level 23 of 30. Should I complete more missions in order to level up before I go through the the Omega 4 Relay? Will being a higher level help me earn the "No One Left Behind" achievement?

Neither of these questions make any reference to level:

• How do I earn "No One Left Behind" with as few squadmates as possible?
• Mass effect 2 ending

Unlike combat in Mass Effect 1, level has much less of an impact on combat performance (in part because the skills are, with one exception, all active abilities and not the deluge of passives littered throughout the ME1 skill trees.)

Especially if you're not playing on Impossible, there is no real reason to level up, as it won't make your health or weapon damage decidedly better (and you won't need the extra skill damage to punch through the multitudes of armor/barrier/shields present on higher difficulties). Furthermore, Loyalty is the only deciding factor in the survival of squadmates - level has nothing to do with it.

Let Loyalty, not level, be the sole determining factor on when to go through the relay. Since you already mentioned that your squad is loyal, its time to put your face to the grindstone - get in there and kick some Reaper ass. Good luck!