Sorry I can't contribute, stevenshev, I'm not that familiar with Osaka.

?!?!?!?!

This opinion is not shared be everyone.

Sushi CAN be a casual food.

But this is like saying:

"Tuna in Europe is a rather casual food and mainly a filler in case you are hungry and don't feel like cooking your dinner or lunch."

Someone who is setting out to eat some of Europe's finest tuna would have little interest in that which comes from a 1 Euro can.

There's a world of difference between sushi and GOOD sushi, the OP knows it, and so do the majority of Japanese people. For many households, ordering in a sushi delivery is still a way to mark a special occasion.

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Just looked into this (I love delving through Japanese food sites!). Here is where I might pick if i was in your happy situation.

Shop is blogged about here, webpage has stunning photos: http://blog.livedoor.jp/osakanohonnm.../51154249.html
Shop name is 鮨 さえ喜 （すし さえき - Sushi Saeki)
Address 大阪府大阪市北区曾根崎新地1-5-7 森ビル　１Ｆ - Sonezakeshinchi 1-5-7, Mori Building 1F
MAP
06-6345-7344 (open from 6pm til late)
Price is indicated as being between ￥15,000 and ￥20,000 (the blogger paid ￥15,000)


Sushi Sakae is quite a new restaurant and the blogger says it's an offshoot of Noguchi, a very popular sushi ya in the same neighbourhood (so popular it may require reservations)
Address and details for Noguchi here http://r.tabelog.com/osaka/A2701/A270101/27004965/
In this link you can see that the makisushi piece made of sesame seasoned rice with mackerel rolled in a kombu type seaweed is sold in both places.
The same blogger (Osakanohonma) has an even better review for Noguchi here:
http://blog.livedoor.jp/osakanohonnm.../51254681.html
Price is also indicated as being between the ￥15,000yen and ￥20,000 bracket
More pictures of Noguchi 'fillers' can be found on this page, scroll down a little and you'll see 1 2 3 4 5, each of which can be clicked on for more photos.

The cost of GOOD sushi doesn't seem to soar as high in Osaka as it does in Tokyo. One of the city's most expensive places appears to be
多田 （ただ）Tada
Price is indicated as being between ￥20,000 and ￥30,000
Reviews for this place are consistently good also.
Map and phone here http://r.tabelog.com/osaka/A2701/A270101/27003367/
Address: Sonazakeshinchi 1-5-26 永楽 (Nagaraku?) Linden Building ４Ｆ
And here's another blog detailing their experience at Tada: http://sgourmet.blog94.fc2.com/blog-entry-75.html
The blogger paid around ￥20,000, and interestingly referred to Osakanohonma's (the previous blogger) account of the same restaurant:
http://blog.livedoor.jp/osakanohonnm.../51176242.html
Oops!
It's THIS review that was referred to.
http://blog.livedoor.jp/osakanohonnm.../50888672.html (expect to pay at least ￥15,000)
Osakanohonma seems to REALLY rate this restaurant (from what I can tell using a translation tool, it seems to be considered the best place for sushi in Osaka)
Only nine places, so assistance from the RC concierge will probably be needed to secure a booking, and the sooner the better. Some rather exotic ingredients are used here, learn how to say "I don't eat whale meat" if you'd prefer to avoid it.
Apart from what I've written here, only mention of the place in English on the internet seems to be this one. Gratifyingly, it echoes what I've learned.

All three restaurants are within easy walking distance of the RC.
Personally, I'd contact the RC before arrival and request that they make a booking at Noguchi, but Tada looks really good too!

It would be fantastic if you could report back with your choice and opinion.

EDIT TO ADD - another option here:
http://blog.livedoor.jp/osakanohonnm.../51459501.html
広川 - Hirokawa (price of meal shown was 10,000yen)