I've taken a tour of the apartments at SM Grande with a view to a one year lease around 3 years ago, i'm not aware that they do short term stays under 6 months.
The apartments are ok just normal, fairly spacious with average fixtures and fittings, nothing too special but not too bad maybe 6/10
The pool isnt massive but a good size and is very nice and has a whirlpool jacuzzi next to it, and the gym is well equipped and new.
This apartment hotel is very popular with long term arabic customers and families.
The reception staff i met are not very happy and are not personable at all.
The best place i looked at and i looked at alot of places in soi 6 and 4, was the place opposite Dynasty Grande in soi 6 and one place down the small soi next to the woraburi which may have been called Boss suites, both of these places were plush and very well decorated and operated, but i think thye may only have been doing mid long term contracts, best to do doem research on them.
The Dawin and the Dynasty Grande are ok for hotel rooms, Grande Sukhumvit at the bend of soi6 is also recommended by some BM's here, and not far to soi 8 through the alleyway and past the BJ bar, you can also follow soi 6 to the end at sukhumvit and use the overhead walkway to get to Soi 7 and 5 if you like to avoid nana.
http://www.booking.com/hotel/th/s-m-grande-residence.html