Sorry to hear about Marshall...it's hard to lose a pet at this time of year. Try to console yourselves by remembering the good times and his happy life.
AS for the topic, Rhys's best pal is Lulu, a 75 pound black Lab - they love to play with each other and have been since they were 3 months old (they were born 12 days apart). However, they can't play unsupervised because Lulu can get too rough occasionally (she is - after all - a big, clumsy one year old Lab!

). I guess that's the point - just always keep an eye on them.
Oh, and I should add - Lulu has always been careful around Andy (since both were 1 and current sizes when they met) - It seems that Lulu just "knows" instinctively not to handle her too roughly.