Recommendations on PS2 Mods

[Ebf18]

I recently purchased a PS2 and I wanted to know from the PS2 backup guru and others alike, what mod do you recommend to play PS2 backups. I have heard of the internal mods and external mods, but which ones out there work best?? Also, I have noticed that they say that GS2 or AR2 is needed to play PS2 backups, can anyone tell me if this is really a necessity to get them working?? Thanks for the info in advanve