I'm finding an extension for wholesale that can add different products at once. is compatible with
And the extension is compatible with rwd theme and supports importing products from csv file.
I don't think you're looking for an extension. What you probably need to check out is Magento "Grouped product" feature.
Our Magento Wholesale Fast Order is well compatible with rwd and csv import as your require.
It also supports lots a lot of functions and features for Magento wholesalers.
Check it out: