I use SI strings mostly but would like some other strings to blend with them for a bigger sound.
I have Kirk Hunter Emerald and GPO as well but I find neither works well for blending with SI.
As Giga is my main sampler I am looking at Giga options first but considering others too. The only Giga option still available these days besides SI is Miroslav Vitous from ilio.com.. The string demos of that don't sound too bad but it's hard to judge from the demos how well it would blend with the SI strings, plus it's older and only 16 bits.
VSL Vienna Instruments would be a second option, appasionata or the like. I like the sound of the Appasionata strings overall but worried that blending them with SI would result in a string section that sounds "too big", and alternating Appasionata with SI may sound like two different orchestras.
I'd buy GOS in a heartbeat if it was still sold.. the demos of that sound pretty great. (I know GOS2 is eventually coming out but it's a lot less attractive an option to me because it's not Giga)