I'm more familiar with sushi restaurants in Costa Mesa area and can make a few recommendations.
If you're willing to spend $35-50, I highly recommend omakase at Sushi Shibucho. If you sit at the table, it's around $35. For sushi bar, it'd probably be around $50. Just ask for omakase and let the chef do the rest.
If you'd prefer to spend $20 or less, I recommend Kaisen Kaiten Sushi Bar, which is actually in Santa Ana but next to South Coast Plaza on Bristol. This is a conveyor belt sushi bar and the prices are very reasonable. Quality is much higher than Kura.
For fusion dishes, Zipangu in Costa Mesa is ok, but their sushi is not. Their sister restaurant is Ayame at Orchid Hills center in Irvine.
Bluefin is in Newport Beach and their omakase is $35 for lunch and $75 (?) for dinner. A little pricey but not that expensive.