Funkydunk already has a mod for allowing product options on the products listings page.
http://www.prodynamix.co.uk/customer/product.php?productid=2
As for the wholesale qty breakdowns, this should be built into x-cart as it will display a table of quantities with prices.
Here's an example:
http://www.modchipstore.com/PS2_Slide_Card_and_Swap_Magic_v30_20_Combo_p_16158 .html