Started out ok...at my wits end now...

Ok, so my boyfriend and I have had our black cat, Ichabod since he was a kitten and he's now about a year and a half. The place we were living in before had another cat and he and Ichabod would cuddle, play, no worries. We decided it was time to move out and separated Ichabod and the old cat- and adopted a 5 month old kitten (who was named "Loki" for his mischievous behavior) for him as a companion. He was pretty irritated about it for about a month after we moved into the new apartment, but then he leveled out and everything seemed fine. They play, groom each other, pounce- seems they are getting along fine.
   
We're now two months in the new apartment and for the past two weeks (consistantly) and one week before that he only did this once-- Loki has started using two out of three beds in the apartment as his litter box. I think in the past week I've had to change the sheets on my bed about four times. We had him neutered about two weeks ago (everything went fine- he had a check up- surgery went perfectly)
   
I feel exhausted in trying to get him to stop. We've locked him out of the rooms, we've bought them each their own litter boxes, we clean the boxes each day.
   
Earlier tonight we saw him squatting on the bed, getting ready to "do his thing", chased him away with a stern "NO!"
   
About 60 seconds later I come back to the room and he jumps off the bed- leaving us a pleasant surprise on the clean bed.
   
-He isn't pooping and peeing on our roommates bed (he tends to sleep in his room), just on our bed and the couch-bed-thing we have in our living room.
   
-Litter brand hasn't been changed
   
-It isn't medical (so far- they can't see anything wrong with him)
   
-He still comes up to us to be pet and held, so I'm assuming he isn't upset with us over anything as he sill wants to be near us often.
   
-He isn't responding to any scolding or anything.
   
He's super adorable and Ichabod and our whole family is emotionally attached to him- but it's getting to be too much. After the incident today we were all discussing finding him a new home because he just won't stop and doing 4-7 loads of laundry a week, solely consisting of bed sheets and blankets, is starting to get noticeably expensive.
   
PLEASE help. We're all so frustrated and would hate to give him up.
   

Steps to take until this is solved:
   
Buy a waterproof mattress cover for the bed, & a waterproof throw for the couch-thing, to prevents worse damage to the stuffing.
   
Buy Nature's Miracle or another very strong odor & stain remover (pet store) to clean up after the cat.
   
Possible solution:
   
Ichabod may be barring Loki from the litter box, since Loki's getting older (it's a male-competition thing). Get a second litter box. Some cats hate to share. This is the easiest & quickest thing to try. Put the second box in a different place. Also clean the existing litter box with a cleaner with bleach (like Soft Scrub) & add new litter, to start them both off fresh.
   
If this doesn't work, ask me about Extreme Aversion Therapy.