Adding half inch width at the same +34 offset would mean 1/4" or 6mm extra ok the inside & outside.
Increasing to +43 offset would then shift you 9mm inward, so the inside edge of your wheel would be 15mm (0.6") further inward, while the outer edge would be 3mm (1/8") further inward than stock.
If you add 10mm spacers like Volfy mentions (making your wheels 8.5" +33), your outside edge will be about 7mm or 1/4" further out than stock.
Our stock wheels are fairly tucked, with a 20mm spacer bringing them about flush, so I think anything in the 10-20mm range would fit well. But if you go closer to 20, you'll want to add 10-15mm to the rears as well.