What do the rest of your pitchers look like? Kimbrel has been pretty solid this year so far on the saves, i'm not a big fan of Lowe but he's a decent pitcher, Kemp is having a great season so far IMHO, where as HanRam hasn't lived up to his draft hype this year. Buchholz has been doing better this month then April, but I'm not completely sold on him yet, but I think he's got the slight edge over Lowe.
Without seeing your other pitchers, IMO its a Matt Kemp/Craig Kimbrel for HanRam trade...at the begining of the year I would say yes thats a win for you, but based on thier numbers through 2 months of the season, I'd probably stay put.
*HanRam also got beaned in the foot last night, according to ESPN he's DTD with a foot contusion.
Hope this helps.