Gulftown is exclusively the 6 core s1136 32nm chips.
The cheaper (generally better value) s1366 i7 CPUs are called Bloomfield.
Comparing SB to Bloomfield, it generally depends what you want to do. SB is faster clock-for-clock, faster clocked, overclocks higher (when using K series chips) uses less power, is cooler and uses newer tech motherboards.
However, the benefit bloomfield has over s1155 SB is that these chips are limited to dual channel memory (triple channel on s1366) and x8x8 CF/SLI (x16x16 on s1366). Whether this difference in features affects your performance depends entirely on you usage, but generally the real-world performance difference due to these features is very small.
The cheapest P67 boards look like they will be available for just over £100 (however most of these will just have x16x4 SLI/CF - so not great for multi-gpu use). If you want "proper" x8x8 CF/SLI then you will need to pay a bit more (most likely starting around £140),