Buy bioware points?

I have 320 Bioware points, enough to buy two appearance packs in ME2 or ME3 (I only have Mass Effect in my game library.)  But I'm not an appearance-pack-buying kind of guy.  I'd like to buy the two big DLCs (Citadel and Omega), but am only offered 1200 or 1600 points.  How can I get 2080 points?  I recall there being 560 points and other oddball amounts, and I used them to buy very specific amounts of points (which I ended up not using for what I'd intended at the time.)  But now I'm stuck with a "handful of loose change," as it were.

But if I wanted to buy, for example, just the Aegis Pack, at 160 Bioware Points, would I be offered lower amounts of points (if I didn't already have 320)?