Max block is a personal preference. Some like it, some don't. Otherwise, I call the max-block discussions "the eternal debate" - it goes on forever & ever & ever and no one has proven either to be a definitive answer (because there IS no definitive answer). The only semi-consistent recommendations are:
1) if you plan to try PvP with this sorc (especially if you'll be fighting melee/bow chars), then max-block is probably a great idea.
2) if you're using an 'adds FCR' shield like 'Spirit' or Lidless Wall, these tend to have such crappy base-blocking chance that max block isn't worth it (i.e. your end-life will likely be so low that you're still extremely fragile).
As for which shield. If you pursue max block, then I'd probably pick one of these four:
1&2. Need resists? Use a 'Sanctuary' Troll's Nest or 2x PDiamond Moser's Blessed Circle?
3. Plan to be in melee range a lot? Stormshield
4. Otherwise, I'd probably use an upgraded, PDiamond Visceratuant.
And if you don't want max-block, 'Spirit' monarchs are pretty hard to beat.