My experience with Epic level rules is limited (21st thru 24th). So long as you refrain from Epic spells (a good idea; they are a mess! ....manipulating the craft DCs is too easy!), it's not so bad. That way the rules are (essentially) the same as 1-20th, but just more powerful.
As you've noted, Improved Spell Capacity is one route. You might instead want to look into Epic feats that improve your existing spell casting, such as (my favorite) Multispell. Who says you can only do one quickened spell per round?